This is a must have book, ideed, if you're running your games in the setting. Sometimes, building your own setting can be tiresome after all, as this book comes with dozens of cities covering numerous niches of the fantasy genre. Yet, I would also recommend this one for those that would like an inspiration to create their own world.
The book will go through the Inner Sea Region, the central stage for the Lost Omens setting, and it won't go in deep details as the Inner Sea World Guide did back in 1E. Yet, it will give you a good overview of the setting main nations, mentioning important characters, cities, events from the distant past or those that happened during the 1E adventures.
It's a good introduction to the setting and to the Lost Omens product line. I would slove to see more books like this one covering the other regions and continents of the setting.
I have all the stat-block books of the RPG line (except from Bestiary 6 =/ ). They are a must to me, as I don't want to expend my time creating foes again and again, and when I do create them, its good to have some examples.
There are dozens of NPCs in this book, with all sort of different classes (from hybrid classes to occult classes, or just the classic ones as well).While the classic NPC Codex arranged the many characters in it by "character class", this one arranges them by "Organization". The characters are all built to suit a sort of villainous theme, from evil cultists to secret society members to vile arcane scholars to evil druids. There are even pirates and thieves!
Villain codex has new gears, new spells, and some other options - the NPC Codex doesn't. These options to customize the villainous NPCs are also arranged by "Organization". You can also easily rearrange the members of the many Organizations to make new organizations, and the book gives some guidance on how to do this. Like this, you can use this book to insert many different foes in your campaigns "on the fly" (they are all ready-to-go NPCs, just like the NPC codex). Its ease to change their race, some class options, and the flavor, so you can adapt them to any setting or adventure.
The main point of the Villain Codex is, as with any "stat-block" book (Bestiary, NPC Codex, Monster Codex), to provide GMs with characters that are ready to be used on the table. There are some of options that can be used by players as well. You can somehow look at the characters in it to see how you would build your own Villainous NPCs, or maybe player can look at them and see how they would develop their characters class build.
Many are the ways you can use this book. I have it, and I use it all the time.
Unfortunately, I will be taking one star out of the five I wanted to give this book, as I believe we could get more high CR/level villains, to use as really powerful main antagonists in our campaigns. The most powerful ones in the book are CR 14... Powerful, but not so powerful.