When I'm reading fiction, especially genre fiction like romance, I can get through books pretty quickly. If I'm reading serious non-fiction books, it takes me much longer to finish. That's because, as a previous poster mentioned, I highlight, make notes, check footnotes if the book has them, etc. With fiction, I can read straight through and just enjoy it. Not that I don't enjoy non-fiction. However, with non-fiction, I tend to chew on what I'm reading more.
So if someone wants to really just get into reading for reading sake, reading fiction, especially genre fiction, might help.
ETA: To get some recommendations, a site like Goodreads is useful. Also, your local library might have a subscription to NoveList. This database will allow you to search for books based on genre, author, common characteristics like "strong female characters" and more.
Literature Map is also a good site. Here you enter the name of an author you like and the site will give you a cloud like map of similar authors. The closer an author's name, the more similar they are to the original. HTH.