Collector Series Book Thirteen presents new options for the Psion class (from WoTC's Psionics Handbook and Expanded Psionics Handbook). The book includes new character options, prestige classes, feats, skills, and spells.
It also offers new magic items and equipment tailored to help make your Psion more versatile.
There are also sections with archetypes and role-playing tips and suggestions to make your Psion more interesting.
There are also sections on psionic diseases and parasites, crystal palaces, altered states, and the psionic accord.