I’m looking for a sci-fi book series for my dad’s Christmas present.

Book series for adults with little to no romance in it or at the very least not smutty.
He likes the Harry Potter series, Star Trek, Star Wars, The Hobbit, Lord of the Rings, Game of Thrones stuff along those lines.
He also likes alien books and zombie books!
Stuff like that but he doesn’t like romance or “young people” books if that makes any sense? If you have any suggestions that would be great!

by Usual-Opportunity113