Can depend on what you're interested in. There's lots of books on various celestial bodies or overviews of cosmology/astrophysics. A common goto is "a brief history of time" by Stephen hawking. I havent read that in a long time, but in middle/high school I really liked it.

There's also mission/program specific books like "Chasing New Horizons" (about the New Horizons mission to Pluto), or "Failure is not an Option" by Gene Kranz. Plus tons of biographies in various figures in space.