Heat Wave was not a serious read so I'm not going to give it a terribly serious review. I will simply say that, much like it's originating series, it was a lot of fun.
A few simple things that I absolutely loved: there is a doppelganger for every series regular and they all have the same quirks, use the same banter, and do the same moves so it feels right at home. And the Castle doppelganger? His name is Rook. How great is that? It's so obvious but it made me so happy, I can't even tell you.
It doesn't play out exactly like an episode of Castle; there are a few key differences. Number one: Castle goes a lot quicker so the cases aren't as complicated. Because this story had an entire book with which to play out the action there was a lot more going on: more suspects, more murders, more cases that end up being involved and more false endings. The general line-up was the same in that the first suspect you meet is never the person who did it and the climax involves a life-threatening situation that is happily resolved; but there was a lot more detail to this case then you generally find in a Castle ep. (Though I could easily see it as a two-parter.)
My main beef is that I imagine Castle to be a better writer than the writer of this book seems to be. Or at least a more crime-focused writer. This story had the tell-tale signs of a crime novel but it lost me in the romance department. First off, it took Castle four full seasons just to get a steamy kiss in with his ingenue. And secondly, the sex scene that the book jumps right into is straight out of a harlequin romance novel complete with firey metaphors and overly dramatic language. Bleh. There's also a lot more fluttering hearts and body-tightening glances than I can stomach and I wonder if maybe the series gets away with that better because they're showing rather than telling. Either way, the series is far batter in that capacity than the book.
But, thankfully there is only the one nausea-inducing sex scene and the bulk of the story is the comical banter and crime drama from Castle that I love so I can forgive the writer and still enjoy the story. And while I wouldn't recommended this book to everyone I would definitely recommend it to Castle fans (but I would recommend you skip the sex scene).