Paizo Publishing will release a new Pathfinder Campaign Setting book, Isles of the Shackles, on March 21st.  This 64-page full-color trade paperback covers the pirate islands known as the Shackles, the setting for the Skull and Shackles Adventure Path, which will be in the second of six volumes in March. 
In addition to pirates the Shackles are also home to horrific monsters and savage beasts, and some have ancient cyclopean ruins and lost treasures.  Isles of the Shackles includes dozens of sites for adventures and a large bestiary with numerous beasts and pirate villains. 
The current campaign sourcebook for which this setting can be used, Inner World Sea Guide, has over 50,000 copies in print. 
MSRP will be $19.99.