Eidolons Unbound

From publisher blurb:

The Summoner as presented in the Pathfinder Roleplaying Game Advanced Player’s Guide opens up an entirely new kind of magic, and offers players an entirely new perspective on the game’s major assumptions. Summoners are bound to a powerful outsider called an eidolon- a creature that bridges the gap between animal and god! This sourcebook builds on that strong foundation, providing a host of new options for Summoners, which will allow them to forge spiritual bonds with even more impressive eidolons.