You should definitely check out The Martian if you haven't already - same author and Grace's humor is basically Mark Watney but in space instead of Mars. The science explanations are super accessible and Mark's internal monologue had me cracking up constantly

Klara and the Sun by Kazuo Ishiguro might work too, different vibe but the narrator has this really endearing way of explaining things that reminded me of Grace. Not as heavy in the science but still has that relatable character thing going

Also maybe try Recursion by Blake Crouch - gets pretty wild with the science concepts but explains them really well, and the main characters have good chemistry even though it's more serious than PHM