Which books are most important to learning the setting, not the rules?

Question

I'm an experienced Pathfinder player and GM, but other than a single attempt at play-by-post Rise of the Runelords, I've never actually run anything set in Golarion and not played much more. I want to give my players in my upcoming Mythic campaign free reign to go where they want and do what they want after a short introduction arc, and since creating an entire world from whole cloth is beyond my spare time right now, I've decided the best existing setting to use is the one the game already assumes. However...

...I've never previously purchased setting books, not even in PDF format, and I need to get up to date fast. Which books or PDFs are most important to figuring out Golarion, so I can get started in the right place?

If it matters to your answer, we'll be starting near the north-eastern coast of Katapesh, as the published adventure I'm going to start with is set there. After that's done I have little ability to predict what will draw my players.

Answer 1

Inner Sea World Guide

This book is meant to be the egg-laying wool-milk-sow (if I may use translated German idioms) regarding the Inner Sea Region, the main focus of Golarion (despite the name, this region extends quite far into the north of the Inner Sea). That means, it introduces just about everything, at the expense of detail that is found only in the more focused Campaign Setting books.

It contains an overview over (non-inclusive list)

• Races of Golarion (including the different humans, such as Chelaxian, Keleshite or Vudrani) and their relations with another.

• A brief overview over every nation in the world, about 4 pages each, for a total about 170 pages. These provide insight into the most important landmarks and characteristics and typically include a ½ page map. However, detailed descriptions of cities (or even maps) can not be found in this book.

• Major history of Golarion, including mythical history (such as the entrapment of Rovagug), up to the recent past. It does not include more recent events such as the most recent Crusade against the World Wound.

• Description and portfolio of the major gods (½ page each), as well as brief paragraphs concerning the archfiends and similar god-like creatures such as the Four Horsemen, the Eldest, and the Elemental Lords. As well as a couple of non-religious philosophies.

Other books of interest

There is not much to suggest beyond this book, as it really depends on where your players are headed (or on how well-filled your wallet is and how fast you can read). There are a handful of books about specific topics, as well, such as Inner Sea Gods (another 300 page book) or the smaller (64 page) Inner Sea Magic/Combat/Knights. Most of the other books or booklets about the setting focus on specific areas or organizations.

Lastly, should your guys decide to travel half-way around the world, the pseudo-asian continent of Tian-Xia is described in the Dragon Empires Gazetteer.

Answer 2

The Inner Sea World Guide is your best starting point to get lore on the entire region, and Inner Sea Gods is second after that to understand the religion and cosmology. But those might not be the best place to start.

Paizo has a lot of setting splatbooks for specific regions. So if you're starting in Katapesh, you would do well to start with Dark Markets - A Guide to Katapesh, for example. It's not like new PCs can just go anywhere they want without any notice, so you will get going in your campaign the most quickly by getting the couple Campaign Setting or Player Companion books about the one or two regions you plan to kick around in. Most PCs spend their entire "lives" inside one or a handful of regions, so a lot of the content in the ISWG will be interesting to you but not directly relevant to them.

Feel them out ahead of time. I'd be surprised if they didn't want to go to Abasalom as the biggest, baddest city between Katapesh and everywhere else, for example. The ISWG is great but you get a couple pages per country, if you can plan where they're going you can get the much deeper treatments of those places in time to use them in game.

Also, I'll be honest - your PCs will move around a lot less if the places they go have interesting depth and detail. Country-hopping by PCs looking for thrills generally is a result of the previous country being really boring, unless there's something specific and questy sending them on that path.

So I instead recommend the following order.

1. Setting book for your starting region (e.g. Katapesh) - or, if there's an Adventure Path set in that region, the adventure path (whether you run it as an adventure or not it's chock full of setting info)
2. Setting book for any specific regions you plan to go to as part of your campaign (including the planes, the planets, etc.)
3. Inner Sea World Guide
4. Inner Sea Gods
5. Everything else

Also note that the Pathfinder Wiki has large amounts of setting information if you need to go look something up. (Don't use the old wikia one, they moved the site but wikia won't let people close down or delete defunct sites because they like the SEO and ad revenue.)

Answer 3

In order of importance, in my opinion.

Inner Sea World Guide

Inner Sea Gods

And then probably any of the "races of golarion" player companions depending on which races you want to learn about.

If just humans, the ISWG covers that pretty well. And the Inner Sea Gods is probably one of the best lore books after that because it goes into so much detail about the gods and the areas that worship them.