Sirius
the first Amber series is GREAT, the second is OK or crap depending who you ask.
Pope
At the center of reality is the land/kingdom/universe of Amber. Emanating from it are the Shadows -- other universes or realities -- and members of the royal house of Amber have the ability to walk from one Shadow to the next. In an infinity of Shadows, any world that can be imagined exists somewhere. (Or perhaps they only come into being when they are imagined; is there any way to know? In either case, knowledge and imagination seem to impose limits: There is no indication, for instance, of anyone being able to walk to a hypothetical world of super-advanced technology and bring some of that technology home.) In some sense, though, Amber itself is more 'real' than the Shadows, and when Oberon, its ruler, disappears, it is for Amber that his nine sons compete.
Corwin, the hero of this story, is competing at a particular disadvantage: Most of his opponents don't know that he has lost his memory, and is running a very long bluff. In the process of his relearning his way through Shadow universes and shadow politics, the reader is also introduced to this fascinating and ambitious setting. "Nine Princes in Amber" is the first and best of the series. The story goes on too long as, in the succeeding novels, "The Guns of Avalon" (***), "Sign of the Unicorn" (**), "The Hand of Oberon" (**), and "The Courts of Chaos" (**), the story becomes more and more convoluted, and Corwin works out who is betraying what to whom.