I'm really enjoying Project Hail Mary, the new book from The Martian author Andy Weir, and I think other LW readers might as well. 

Avoid spoilers harder than you normally would -- there are a lot of spoilers online that are easy to hit by accident.

Why you might like it:

• Lots of figuring things out on the fly; math, science, and general hypothesizing / problem-solving exercises. Fun to stop and try to figure out on your own, or just relax and watch the character solve them.
• Requires a lot less physics knowledge than some similar books to "play along at home" (e.g. I could do most of what I've seen so far, vs. something like Egan's Orthogonal, which needs more physics than I know)
• Nice escapism about how Earth responds to global threats :)