The new pocket editions of Pathfinder have me thinking about how I might approach a return to Pathfinder for a future campaign. The simplest and most productive means of returning to Pathfinder (as I see it) is to apply minimalist philosophy to the process. For me, that means figuring out precisely what books are necessary to the process....my list would look like this:
Bestiary II (it has the cool planar stuff)
Bestiary III (it has the cool non-western monsters that I used heavily)
...and maybe the Gamemastery Guide (for general GM utility)
And that would be it. Although....I'd be tempted to check out the new Horror Adventures book, too. But that's the Pathfinder trap! There's always one more book worth looking at.
My players might fret over an absence of the Advanced Player's Guide or Complete Magic and Complete Combat books, but honestly, if there's something in there that really needs to be at the table for some reason I can look it up on the OGL site.
Books I would absolutely exclude because they change the fundamental focus of the game or move away from the clean path of a "one core book to rule it all" approach: all of the Ultimate books, the Pathfinder Complete books, every single splatbook ever, the Mythic Adventures book, anything 3rd party Psionics related.....none of that is essential or (at this point) even desirable for a more focused core book style campaign.