From publisher blurb:
A Rumble in the Jungle
On a sweltering jungle planet around a dying star, ape oracles and simian scholars study the natural rhythms that pulse through the planet like a heartbeat, giving birth to an incredible array of titanic kaiju crawling from the planet's underworld. Kaiju cultists strive against sinister insectoid aliens to control the uncontrollable gargantuas while the tree cities of the ape-lords desperately try to keep the peace on Jowchit! You'll find new class options, drugs, and feats await, along with a detailed planetary gazetteer, adventure hooks, a new playable race, and the mystical Jowchit girallon!