This book is ostensibly written by Richard Castle, a fictional character and main protagonist of the TV show Castle. He's supposed to be a James Patterson, Dean Koontz, Tom Clancy style blockbuster author, with a focus on Mystery Thrillers. Heat Wave is, within the context of the TV show, the novel he writes over the course of the first season, using the show's other main character as inspiration; Kate Beckett, an NYPD detective.
However, this book is really more of a book written by 'some guy' inspired by watching the TV show than by 'Castle' inspired by Beckett. Every character in the book has a direct analogue to the TV show, to the point where the book may as well not have even replaced the names. Within the context of the book, there's a journalist following Nikki Heat around named Jameson Rook... yeah. Heat and Rook have an intense attraction to one another hiding behind a veneer of sarcasm and mild resentment (on her side at least)
So really, it isn't actually a book, it's one episode of the TV show in book form. It's not a terribly good episode either. The plot unfolds so predictably that it's almost painful. The millionaire industrialist is actually broke. His trophy wife is a former stripper. The virtuous accountant is less than virtuous. The crazy Russian giant loses an identifiable ring in a key location because he needed to lose it there to connect the two crime scenes. The only original idea comes near the end, and it's the only salvagable part of the experience.
Overall, it doesn't read like a book written by the character Richard Castle would, it doesn't give fans of the show anything new for these characters to do, and the plot is noticeably less intelligent than plots on the show tend to be. All the humor falls flat as does the romance. The action scenes are okay though, and those are hard to write. Skip this book and watch the TV show, after all, it stars Nathan Fillion. If you watch it all and can't wait to watch more, the book might be worth your time... all 3ish hours it'd take to finish. It's only about 180 pages long.