The Bloodline Feud

I quite enjoyed The Bloodline Feud. It is great writing and a very good story, but it doesn't fit easily into a genre – call it a sort of a speculative-fiction, techno-thriller, crime-fiction crossover. It is an exciting romp with alternate-Earths, deadly feuds, and a ton of action and intrigue. It actually reminded me quite a lot of Roger Zelazny's Amber books.
(Fair warning: The Bloodline Feud is a re-edited omnibus edition of a story that was originally published as The Family Trade and The Hidden Family.)

Update: Even better on a re-read. I finished it thinking of snarky alternate titles like Miriam in Wonderland and Looking Glass 2.0.