From the back of the book:
We all dream. For some, dreams can become reality. This book provides everything needed for Call of Cthulhu investigators to travel down the seven hundred steps through the Gate of Deeper Slumber and into the land of dreams. It includes a travelogue of the Dreamlands, a huge gazetteer, statistics for over thirty prominent NPCs, a bestiary of over sixty monsters, information on the gods of the Dreamlands and their cults, a fold-out map, and more. Also present are two adventures, Lemon Sails and Pickman's Student, to help get keepers started adventuring in the Dreamlands.
This fourth edition of the Dreamlands is much larger than previous editions, with almost a hundred pages devoted to new background material and a character generation system. You can now choose to visit the Dreamlands, or stage a campaign there.