Not sure if you're familiar with this chart https://www.thetrekcollective.com/p/trek-lit-reading-order.html?m=1
DS9 Millennium (3 books) is good. Like a future what if end of the universe thing.
New Frontier series (at least 6) is a fun read. Follows after titan era. Not too serious, and some new characters on the fringes of federation space.
An older crossover, Invasion (4 books) is a story told through tos, tng, DS9 and voy. Was fun to see all the familiar characters dealing with the same overall problem.
The fall (5 books) was good. I was looking for something random and started at a recommended spot on the chart. I do feel like I missed a bit that they kept summing up. Probably better to start with the borg invasion if you don't want to feel like you got plopped into like season 3 of something.
The Buried Age was fun, Picard as captain of the stargazer more or less gathering the tng crew.
Can't beat an old TOS random paperback sometimes. Those can be so wacky.
Hope that helps