One-Eyed Jack and the Suicide King are genii loci, the legendary avatars of Las Vegas. The Las Vegas of 2002, that is, because the city's symbology shifts from decade to decade. (And 2002 is roughly when the book was written, says the author.)
We find Jack and the King setting up a ritual at Hoover Dam. It happens that Las Vegas is involved in a mystical war with (no points for guessing) Los Angeles, and an avatar of LA shows up at the Dam to stop them. At the same time, a couple of fictional secret agents find themselves under fire from another fictional secret agent. Their fictional 1964 (the eternal Cold War) leads them to the real-world 2002, at the same time as... I think I won't name the rest of the characters. A large part of the fun is seeing everybody walk on-stage.
I don't necessarily get a lot out of seeing characters walk on-stage. I am not a watcher of the TV shows in question. For reasons of intellectual property, their names are never used, which means long chapters of text about "the athlete" and "the Russian" and "the American" and so on. I had to look some of them up. (Spoiler: it suffices to google "tennis-playing spy".) Yes, the author makes a plot point of how media ghosts are esoterically nameless, but it still feels like playing with action figures.
So the book is fanfic, in fandoms not my own; this makes it a rough ride. It's perfectly good fanfic, and in fact it succeeds at showing me how these characters are delightful. It doesn't rest entirely on familiarity. And the central viewpoint is that of Jack, an original creation. But I'm missing some of the fun, regardless.
It's in the Promethean Age continuity. Like most of that series, it involves a lot of running around for mystical reasons which don't make much logical sense but have solid gut impact behind them. The magic is good stuff. Since it's also a spy story (and a vampire story, and a Western) there's a lot of chasing and gunfights and sneaking around in the desert. So, more accessible than some of the Promethean Age books.
I feel like I'm making random stabs at description without saying very much. I fear this is because I enjoyed the book without loving any part of it. I'll leave it at that. If any of the above sounds like your thing, go for it.