From publisher blurb:

Carl Gleba, author of the popular Phase World®: Three Galaxies™, has created a sourcebook and guide to help Game Masters create their own alien dimensions and worlds. A great tool for G.M.s and fun for players.

Rules, suggestions and tables for generating dimensions.
Dimensional anomalies and other strangeness.
The Shifter “Revisited,” Dimensional Familiars and new O.C.C.s.
Many adventure ideas, including The Mechanoids® and more.