I've never seen so much as a single scene from the Monk television series. So why do I enjoy Lee Goldberg's books about the character so much? Well, let's see. They're funny, they're well-written, they're carefully plotted, and they're poignant. They probably have other good qualities, too, but those should do for starters.
In this one, Monk is called on to solve a murder (or murders) connected with a convention of Earthers, that is, people passionately devoted to a canceled '70s TV series called Beyond Earth, to which, of course any resemblance of any other TV series, living or dead, is purely coincidental. Goldberg has a lot of fun with the Earthers (they don't like being called Earthies), but it's not mean-spirited fun, as we (and Monk) discover as the book goes along. In fact, it leads to Monk's having a breakthrough moment.
As usual, Natalie Teeger's narration is just the right vehicle for the story, and Natalie has a few insights about herself that parallel Monk's breakthrough. Ambrose plays a crucial role, and Monk's relationship with his brother makes a big advance.
You say you don't read tie-in novels? You should give the Monk books a try and find out what you've been missing.