I'm planning on checking out this setting to run it sometime. Apart from the main Adventure Path books are there any others that would be useful either for sidequests, background?
I saw the recommendations in the player's guide:
Inner Sea Primer
Inner Sea Pirates
Sargava, the Lost Colony
I saw as well by browsing
Isles of the Shackles campaign setting
Plunder and peril adventure
Inner sea Magic
Anything else I could be missing? I'm more interested in the Game Master's side so the campaign setting book seems the most likely purchase in any case.
I'd say that Isles of the Shackles is more important than Sargava, the Lost Colony. Plunder and Peril is almost more an alternate chapter one for the AP than a supplement, in my opinion. Inner Sea Magic gives some flavour, but I'd value the Inner Sea World Guide over it, particularly given the scale of the Shackles and how likely it is that PCs will be sailing outside the islands.