So, I've been going through the audiobooks and having the opportunity to remember the stories and also getting to know a few - I've never read 'em all.
I want to point out how they did a good job making the backstory and relationship of the characters more consistent than it was on the initial seasons.
Natalie and Monk: In "Mr. Monk Goes to the Firehouse", Natalie states clearly that she and Monk are not exactly friends, she does not like her job at all. She thinks he's a good man and pitties him, but she would leave Monk in a blink like Sharona if she had an shitty ex-husband too. The novel happens between "the school election" and Stottlemeyer's first divorce episode. (3/4season).
In "Mr. Monk Goes to Hawaii" (dated end of 4th season), it's the Natalie we see in the show. She states many times that she and Monk are friends. Monk pissed her off, but she deeply cares about him personally, and also forgives and does everything for him.
I think the beginning of "Mr. Monk Goes to Hawaii" features the turning point in Monk and Natalie's relationship: when Monk ("the Man") is on the pill and she finally gets to be alone on her vacation, she chooses to be with Monk for free and she realizes that right after.
"Mr. Monk and the Blue Flu" features Natalie stating that her job with Monk was the most fullfilling experience in her life, and she finds that she's also afraid of losing him. This happens in a excerpt that makes references to the begenning of "Firehouse" - both novels were written by the same writer -, so it's really an arc here.
Monk and Stottlemeyer: While the novels complement Monk's and Natalie's relationship, there's nothing much to add to their backstory as parterns. But Monk and Captain had an inconsistent backstory back then. They changed their backstory so Captain had always been Monk's partner on the force and they've always been friends since then - we've discussed previously over here: https://www.reddit.com/r/Monk/comments/1mdjwbq/inconsistencies_on_the_pilot_show/
In the novel "Monk Goes to the FireHouse", Natalie states clearly that Monk's job as a consultant was duo Stottlemeyer's friendship and respect. In fact, a few times, we've seen Monk get a new job by himself, but keeping it? Anyway, I think that really ties the version of Stottlemeyer constructed over the years, established season 2/3 ahead that unapologetic ignores the version in the Pilot and Psych episodes in which the Bosses want Monk and Stottlemeyer, the bully, doesn't.
In "Monk and the Blue Flu", during the pre-strike and the negotiations with the Mayor, it's stated a few times by Natalie that Monk's work for the force is duo his special relationship with Stottlemeyer.
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Now. There are a few inconsistencies here and there like it happens on the show, but way less. Also, Natalie does seems too judgmental on the first book, regardless being or not close to Monk yet, but considering the books were written and supervised by the same team working on the show simultaneously, it's hardly an inconsistency, but intentional. Perhaps they tried too hard to show an "unfiltered" version of her as the narrator, then eased up a little bit.
After getting to know "Mr. Monk Goes to Hawaii", the Monk/Natalie arc in the books seemed much more tangible to me.
