Trumps of Doom by Roger Zelazny

If you get discouraged waiting for the next book in a series to come out, don't feel bad. Zelazny published The Courts of Chaos in 1978, and "The New Amber Novel" Trumps of Doom did not appear in bookstores until 1985. That's a long long time.

Merle Corey is a programmer for a software company called Grand Design, in San Francisco. He has wrapped up his projects and is taking off on sabbatical. As he is wrapping things up, his friend Luke Reynard drops by with a note from his ex-girlfriend, Julia, which prompts Merle to go see her.

The date is April 30, and for the last five or six years, some unknown agency has tried to kill him on that day, for no apparent reason. When Merle arrives at Julia's apartment, he discovers her mauled body, and is himself attacked by a mangey-looking dog analog, which he grapples with, then throws out of a two story window.

Merle is understandably upset by Julia's death, and sets off to investigate the cause, blaming himself a bit. Julia had, from the evidence in her apartment, gotten fascinated with the occult after they broke up, so he heads for the occult bookstore of a mutual acquaintance, Rick Kinsky, to see if he knows anything. Rick tells him that Julia was seeking arcane knowledge that he wasn't able to provide, and she moved on to study under a "master" named Victor Melman, and gives him Melman's address.

When he goes to Melman's apartment to interrogate him, Melman reveals a mural (he's also an artist) on a wall that behaves just like a giant Trump (the cards that transport Amberites from place to place), and is drawn into a confrontation with a cloaked sorceror in a strange Shadow. When he returns victorious from the shadow, Melman attacks him, as well, and Merle ends up killing him before he can get more information.

Zelazny slowly reveals that Merle is actually Merlin, son of Corwin of Amber, and weaves a great tale in the old spirit as Merlin tries to find out who's trying to kill him, has succeeded in killing Julia, and what sort of plots are afoot in Amber this time around. A great return to Corwin's old stomping grounds, and a reunion with the family of Amber.