A society of wizards monitors Castle Timeless, the stronghold of the missing wizard Jelerak, and home to a mad Elder God named Tualua. Wizards from within and without plot to take the castle and the powers of the imprisoned god for their own, until Dilvish arrives with vengeance on his mind...
The Changing Land is a good quick read. Bascially, it's Roger Zelazny telling a pulp swords and sorcery sort of tale with some Lovecraftian elements thrown in. Dilvish and his steel horse Black are an interesting, if underdeveloped, pair. I found Jelerak and the relationship between Semirama and Tualua to be the most interesting parts of the book, although the imprisoned wizards definitely had their moments.
The ever-changing landscape outside Castle Timeless reminded me both of the Amber series and Michael Moorcock's depiction of Limbo in his Eternal Champion saga. The plot, while not overly original, has enough twists to keep it interesting, as well as an ending that I didn't see coming.
The Changing Land is well worth a read but I wouldn't rank it among Zelazny's best works. 3.5 out of 5.