There better be a Bestiary 4. No monster line is ever complete, any TTRPG company should know that! They have more Divs, Asura, Celestials, Behemoths, Kami, Oni, and many other creatures to add more of that they've gone and created.
To top it off, the considerable excitement and buzz which accompanied Frog God Games’ 800 page+ Tome of Horrors Complete for Pathfinder RPG last September left me thoroughly underwhelmed in terms of my own perceived “need” for a Bestiary 3. After all, I already had Bestiary 1 and Bestiary 2, monsters from the various Adventure Path installments, plus many more foes from the various modules and Pathfinder Chronicles released by Paizo over the past nearly three years. Include into that collection the various demonic, diabolic, and daemonic horrors from the three volumes of the “Books of the Damned” and add the massive Tome of Horrors Complete, too? As you might imagine, I was simply not feeling any sharp hunger for yet-another-monster-book for Pathfinder. Fact is, I felt pretty much overwhelmed with monster material for Pathfinder already.
While the stat blocks for the monsters previously presented in the Bonus Bestiary are, for the most part, unchanged, the descriptions of the monsters themselves are different. James Jacobs explained on the Paizo Message Boards that when the Bonus Bestiary was in production several years ago, Paizo had not yet settled upon their format for presenting monsters and were still experimenting with various approaches at that time. The versions of the monsters which now appear in the Bestiary 3 are the “official versions” of the monsters in the Pathfinder RPG and supersede the versions previously presented in the Bonus Bestiary.
The Asian themed monsters in the book are well done and the illustrations are top notch. More importantly, I did not find that their numbers were such that they overwhelmed the book in terms of their quantity or prominence. There are various Imperial dragons, Onis, Asuras and Divs in Bestiary 3, but the total number of Asian themed monsters is probably about 10% of the book overall. If you were hoping for a true “Oriental Monstrous Compendium” for Pathfinder – then you will be disappointed to discover that Bestiary 3 simply isn’t that sort of book. However, if you were in the camp that isn’t terribly interested in Asian themed monsters, then you will not feel put upon or otherwise take umbrage that Paizo has put too much peanut butter into your chocolate. To me, this was a plus. Of course, to others, YMMV. There better be a Bestiary 4. No monster line is ever complete, any TTRPG company should know that! They have more Divs, Asura, Celestials, Behemoths, Kami, Oni, and many other creatures to add more of that they've gone and created.