I just watched the "Nikki Heat" episode of Castle, which was a hoot, and even more so because I'd just finished reading Heat Wave. In the episode, The actress who's to play Nikki Heat in the film version of Heat Wave shows up to do some research into the role by following Beckett around. As Castle notes, it's all very meta. And often hilarious. I enjoyed the heck out of the episode.
I wasn't sure I was going to get through the book at first. The prose tends to the purple end of the spectrum. I saw someone write that it's written like a Dan Brown novel. My own thought was that they probably tries to emulate James Patterson or (the late) Stephen Cannell, who have both appeared on the show as Castle's poker buddies. I don't actually know, since I haven't read any of them.
Anyway, the prose eventually settles down to something a bit more tolerable, and the mystery is a good one. There're lots of meta references to snicker at. Nikki Heat keeps wanting to hear the balding, poker playing Judge Simpson say "D'oh. In the series, the poker playing judge is played by Dan Castellaneta. There's also way more nakedness than on the show. There are worse ways to spend a few hours.