We have used bookadventure.org for years.
I used to look for books on the AR reading list, but have since relaxed way more in our homeschooling endeavors and have dropped the idea of reading levels for the most part... I mean I'm not going to allow my oldest to choose The Cat in the Hat as his reading book for that week (he can surely read it for fun along with his "mom approved" book) but you get my point. If he were to decided to read 3 Magic Tree House books for his weekly reading, then I probably would consider that just as much as I would consider it fine if he chose to read Alice's Adventures in Wonderland (which is what he is reading right now).
Homeschooling DD~9, MDS~8, and YDS~5 and mom to ODS~15 who goes to a tech school.