There's no one in this community yet other than me, but I just figured I'd write a short little post just to start things off.
As a big Sierra fan, especially of the Gabriel Knight (and Quest for Glory Games), I only recently found out that two novelizations were made of the Gabriel Knight series! And well, I also like to read, so I briskly read through them.
The books are Sins of the Father and The Beast within, the first two games respectively. And they're... pretty good! They're essentially a beat for beat telling of the games, with only very occasional detours to say whats on Gabriel's mind, or maybe provide just a little more context and logic to make a video game mechanic make more sense in a written narrative. If you've played the games they're also incredibly fast reads - being basic in their prose and easy to visualize from the game.
Anyway. They are a bit hard to find these days. Sins of the Father goes for $20-25 on secondhand markets, and The Beast Within often has an asking price of $70! I'm guessing the vast majority of the books are largely just seen as pulpy fiction stories to the vast majority of people, so I can imagine that they're quick to get binned and otherwise neglected.
You can still read them online quite easily, and it's well worth it if you're a fan. Might be a good replacement of replaying the games!
I only wish they had made the third game into a book - seeing that it's nearly impossible to run and experience first hand these days.
Let me know if you've read or heard of them!