Hi R.,
My son (10) and I read together often. He is not a big Harry Potter fan. What we have enjoyed are the books by Roald Dahl - Charlie and the Chocolate Factory, Charlie and the Great Glass Elevator, The Twits, James and the Giant Peach. He has a bunch.
Also Kate DiCamillo's Edward Tulane and the Tale of Desperaux were good. We will be reading her Because of Winn-Dixie this summer.
We read a Goosebumps a year or so ago which I looked forward to every night. My son braved it out and told me when I was selecting the next Goosebumps that they were too scary for night time. :0 Those we leave for daytime stories.
You can also check with your sons' teachers. My son's fourth grade teacher sent home a booklist with his recommendations highlighted last summer. I am hoping that this year's teacher will do the same.
Happy Reading.