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"They Can Certianly Try"

If it isn't in some form of code, you can "read" any spell if it is on your spell list just fine as evidenced by the fact that you can read scrolls of spells on your spell list even if you don't know the spell. Which means any cross over your class has with the book, you'll recognize.

If it isn't on your spell list, and you proficient in arcana and the book isn't in code you should be able to try "read" it with something like an arcana check.

Arcana

Your Intelligence (Arcana) check measures your ability to recall lore about spells, magic items, eldritch symbols, magical traditions, the planes of existence, and the inhabitants of those planes.

That doesn't mean you can grasp the spell from the spell book enough to cast it. This will tell you what is written in the book. You'd learn what spells are in the book and their general effect.

Think of it like a research paper or college text book of a subject you're not versed in. You can gleam, "Oh, this is a paper on the Solvent Energy of a Protein in a Dialectic Solution" But you don't have the ability to take action on that unless you're versed in that field.

Casting From It

You can't cast it without fully understanding it. Which, for a wizard, requires studying it and copying it into your own notation into your spellbook which requires time and gold. And then preparing it.

For each level of the spell, the process takes 2 hours and costs 50 gp. The cost represents material components you expend as you experiment with the spell to master it, as well as the fine inks you need to record it. Once you have spent this time and money, you can prepare the spell just like your other spells.

For other classes, knowing that it is a fireball, doesn't allow you to cast it.
Unless it is Ritual, and you have Ritual Caster feat or class feature, then you may be able to cast it depending on your particular ability.

Magic Item Spell Books

Some magic item spellbooks might be the exception to that. The DMG lists a few.

• Book of Vile Darkness
• Tome of Stilled Tounge

These are just fancied up spell casting foci that grant spells, benefits or other effects (Book of Vile Darkness can cause insanity for instance).

"They Can Certainly Try"

If it isn't in some form of code, you can "read" any spell if it is on your spell list just fine as evidenced by the fact that you can read scrolls of spells on your spell list even if you don't know the spell. Which means any cross over your class has with the book, you'll recognize.

If it isn't on your spell list, and you're proficient in Arcana and the book isn't in code, you should be able to try "read" it with something like an Arcana check.

Arcana

Your Intelligence (Arcana) check measures your ability to recall lore about spells, magic items, eldritch symbols, magical traditions, the planes of existence, and the inhabitants of those planes.

That doesn't mean you can grasp the spell from the spellbook enough to cast it. This will tell you what is written in the book. You'd learn what spells are in the book and their general effect.

Think of it like a research paper or college text book of a subject you're not versed in. You can gleam, "Oh, this is a paper on the Solvent Energy of a Protein in a Dialectic Solution", but you don't have the ability to take action on that unless you're versed in that field.

Casting From It

You can't cast it without fully understanding it. Which, for a wizard, requires studying it and copying it into your own notation into your spellbook which requires time and gold. And then preparing it.

For each level of the spell, the process takes 2 hours and costs 50 gp. The cost represents material components you expend as you experiment with the spell to master it, as well as the fine inks you need to record it. Once you have spent this time and money, you can prepare the spell just like your other spells.

For other classes, knowing that it is a fireball spell doesn't allow you to cast it - unless it is a ritual, and you have the Ritual Caster feat or an appropriate class feature, then you may be able to cast it depending on your particular ability.

Magic Item Spellbooks

Some magic item spellbooks might be the exception to that. The DMG lists a few.

• Book of Vile Darkness
• Tome of the Stilled Tongue

These are just fancied-up spellcasting foci that grant spells, benefits or other effects (Book of Vile Darkness can cause insanity, for instance).

Simply Reading it.

If it isn't in some form of code, you can "read" it if it is on your spell list just fine as evidenced by the fact that you can read scrolls of spells on your spell list even if you don't know the spell.

If it isn't on your spell list, and you proficient in arcana and the book isn't in code you should be able to try "read" it with something arcana check.

Arcana

Your Intelligence (Arcana) check measures your ability to recall lore about spells, magic items, eldritch symbols, magical traditions, the planes of existence, and the inhabitants of those planes.

That doesn't mean you can grasp the spell from the spell book enough to cast it. This will tell you what is written in the book. You'd learn what spells are in the book and their general effect.

Casting From It

You can't cast it without fully understanding it. Which, for a wizard, requires studying it and copying it into your own notation into your spellbook which requires time and gold. And then preparing it.

For each level of the spell, the process takes 2 hours and costs 50 gp. The cost represents material components you expend as you experiment with the spell to master it, as well as the fine inks you need to record it. Once you have spent this time and money, you can prepare the spell just like your other spells.

For other classes, knowing that it is a fireball, doesn't allow you to cast it.
Unless it is Ritual, and you have Ritual Caster feat or class feature, then you may be able to cast it depending on your particular ability.

Magic Item Spell Books

Some magic item spellbooks might be the exception to that. The DMG lists a few.

• Book of Vile Darkness
• Tome of Stilled Tounge

These are just fancied up spell casting foci that grant spells, benefits or other effects (Book of Vile Darkness can cause insanity for instance).

"They Can Certianly Try"

If it isn't in some form of code, you can "read" any spell if it is on your spell list just fine as evidenced by the fact that you can read scrolls of spells on your spell list even if you don't know the spell. Which means any cross over your class has with the book, you'll recognize.

If it isn't on your spell list, and you proficient in arcana and the book isn't in code you should be able to try "read" it with something like an arcana check.

Arcana

Your Intelligence (Arcana) check measures your ability to recall lore about spells, magic items, eldritch symbols, magical traditions, the planes of existence, and the inhabitants of those planes.

That doesn't mean you can grasp the spell from the spell book enough to cast it. This will tell you what is written in the book. You'd learn what spells are in the book and their general effect.

Think of it like a research paper or college text book of a subject you're not versed in. You can gleam, "Oh, this is a paper on the Solvent Energy of a Protein in a Dialectic Solution" But you don't have the ability to take action on that unless you're versed in that field.

Casting From It

You can't cast it without fully understanding it. Which, for a wizard, requires studying it and copying it into your own notation into your spellbook which requires time and gold. And then preparing it.

For each level of the spell, the process takes 2 hours and costs 50 gp. The cost represents material components you expend as you experiment with the spell to master it, as well as the fine inks you need to record it. Once you have spent this time and money, you can prepare the spell just like your other spells.

For other classes, knowing that it is a fireball, doesn't allow you to cast it.
Unless it is Ritual, and you have Ritual Caster feat or class feature, then you may be able to cast it depending on your particular ability.

Magic Item Spell Books

Some magic item spellbooks might be the exception to that. The DMG lists a few.

• Book of Vile Darkness
• Tome of Stilled Tounge

These are just fancied up spell casting foci that grant spells, benefits or other effects (Book of Vile Darkness can cause insanity for instance).

Simply Reading it.

You can "read" it if it is on your spell list just fine as evidenced by the fact that you can read scrolls of spells on your spell list even if you don't know the spell.

If it isn't on your spell list, and you proficient in arcana and the book isn't in code you should be able to try "read" it with something arcana check.

Arcana

Your Intelligence (Arcana) check measures your ability to recall lore about spells, magic items, eldritch symbols, magical traditions, the planes of existence, and the inhabitants of those planes.

That doesn't mean you can grasp the spell from the spell book enough to cast it. This will tell you what is written in the book. You'd learn what spells are in the book and their general effect.

Casting From It

However, you can't cast it without fully understanding it. Which requires studying it and copying it into your own notation into your spellbook which requires time and gold.

Copying a Spell into the Book. When you find a wizard spell of 1st level or higher, you can add it to your spellbook if it is of a spell level you can prepare and if you can spare the time to decipher and copy it.

Copying that spell into your spellbook involves reproducing the basic form of the spell, then deciphering the unique system of notation used by the wizard who wrote it. You must practice the spell until you understand the sounds or gestures required, then transcribe it into your spellbook using your own notation.

For each level of the spell, the process takes 2 hours and costs 50 gp. The cost represents material components you expend as you experiment with the spell to master it, as well as the fine inks you need to record it. Once you have spent this time and money, you can prepare the spell just like your other spells.

And then preparing it:

Preparing and Casting Spells

The Wizard table shows how many spell slots you have to cast your wizard spells of 1st level and higher. To cast one of these spells, you must expend a slot of the spell’s level or higher. You regain all expended spell slots when you finish a long rest.

Unless it is Ritual, and you have Ritual Caster feat or class feature, then you may be able to cast it depending on your particular ability.

Magic Item Spell Books

Some magic item spellbooks might be the exception to that. The DMG lists a few.

• Book of Vile Darkness
• Tome of Stilled Tounge

These are just fancied up spell casting foci that grant spells, benefits or other effects (Book of Vile Darkness can cause insanity for instance).

Simply Reading it.

If it isn't in some form of code, you can "read" it if it is on your spell list just fine as evidenced by the fact that you can read scrolls of spells on your spell list even if you don't know the spell.

If it isn't on your spell list, and you proficient in arcana and the book isn't in code you should be able to try "read" it with something arcana check.

Arcana

Your Intelligence (Arcana) check measures your ability to recall lore about spells, magic items, eldritch symbols, magical traditions, the planes of existence, and the inhabitants of those planes.

That doesn't mean you can grasp the spell from the spell book enough to cast it. This will tell you what is written in the book. You'd learn what spells are in the book and their general effect.

Casting From It

You can't cast it without fully understanding it. Which, for a wizard, requires studying it and copying it into your own notation into your spellbook which requires time and gold. And then preparing it.

For each level of the spell, the process takes 2 hours and costs 50 gp. The cost represents material components you expend as you experiment with the spell to master it, as well as the fine inks you need to record it. Once you have spent this time and money, you can prepare the spell just like your other spells.

For other classes, knowing that it is a fireball, doesn't allow you to cast it.
Unless it is Ritual, and you have Ritual Caster feat or class feature, then you may be able to cast it depending on your particular ability.

Magic Item Spell Books

Some magic item spellbooks might be the exception to that. The DMG lists a few.

• Book of Vile Darkness
• Tome of Stilled Tounge

These are just fancied up spell casting foci that grant spells, benefits or other effects (Book of Vile Darkness can cause insanity for instance).