What does he like and what grade is he going into? I'll talk to my librarian buddies & see what they recommend. And try a how-to book. Reading instructions while building something cool or doing something neat is still reading!
I completely agree with MROO. There are a ton of good books out there aimed towards younger boys and getting them to read more. Legos (fabulous series of books on how to build anything Legos, history, all kinds of fun books) Star wars (and all the spin offs), Captain Underpants (very funny, on TV too) Diary of a Wimpy Kid, Geronimo Stilton (a whole series based on a mouse who is a writer and goes on worldly adventures) heck even the old Charlie Brown books.
Libraries are dicey right now but I shop at these places when I want a physical copy-
Thriftbooks.com
https://www.thriftbooks.com/
and BetterWorldBooks.com
https://www.betterworldbooks.com/
So many books are just $4, nice books too not just paperbacks. One places lets you accrue points towards free books and the other takes a portion of their business and donates books to those in need. Both have free shipping over $10 too. I often can get 3 or 4 books for only $12 and I'm always buying gardening, cooking, how to's, quilting, sewing, special interest books for kiddo etc.... books that are normally $20-$30 new on
Amazon or $15 used on
Amazon. If they are out of a particular book you can sign up for a notification/put it on your wishlist and when they get it you'll get an email so you can scoot over there and get it before anyone else does.
I'm a total bookaholic, as in I walk out of the library with usually 20 or more books at a time and up until the lockdowns almost always have library books around the house. Mostly non-fiction, and even audio books if I'm doing a painting project, though those are easy to get on the library's Overdrive page.
Another thing I've done with kiddo is a lot of the assigned reading at Jr high and HS have been made into movies these days. Like The Giver, The Lovely Bones, or Holes and I'll put them on but not really pay attention to them so kiddo has to answer my silly/pesky questions about the characters, the plot, or whatever I can think of that is not a yes/no question.