Can a warlock with the Book of Ancient Secrets eldritch invocation copy spells from a spell scroll from another class' spell list? For example: could a level three warlock copy a spell scroll of detect magic (a 1st-level spell)?
My confusion arises because the spell scroll rule (DMG p. 200) states:
If the spell is on your class’s spell list, you can read the scroll and cast its spell without providing any material Components. Otherwise, the scroll is unintelligible.
And the warlock rule for the Book of Ancient Secrets eldritch invocation (PHB p. 110) states:
On your adventures, you can add other ritual spells to your Book of Shadows. When you find such a spell, you can add it to the book if the spell's level is equal to or less than half your warlock level (rounded up) and if you can spare the time to transcribe the spell. For each level of the spell, the transcription process takes 2 hours and costs 50 gp for the rare inks needed to inscribe it.
Can a warlock transcribe an unintelligible spell, or are such spells intelligible to warlocks with the invocation?