My thoughts are that he’s strongly auditory, possible vision issues(?), but unlikely if he’s not complaining of headaches and is easily reading other things; maybe, as a boy, he wants his momma to do the hard stuff for him (I say that will all due deference as I have a boy who, although it’s not in reading, he loves to let the women around him do the hard stuff!).
IMO, no; what you’re asking isn’t too much at all. I assume he’s both capable of the Robinson Crusoe by Baldwin (I know which one you’re talking about) and definitely the Busy Times, which is simpler. I think this is the age, if he’s an average 8 yr. old reader and not obviously delayed, then we stop doing all their reading for them.
However, a change in style may work. When my son (and DD, whose very auditory), were that age, I had them read-aloud to me a chapter from one of the Pathways (no narration required), their Elson Readers (narration required), Reading Lit. Readers by Treadwell (narration required) and poetry (no narration, just an occasional-“what do think that was about?”). That way, as newer readers, I could hear the way they read, correct mispronunciations, encourage correct emphasis in certain sentences (exclamations, questions, pausing appropriately, etc) and for my dd, as a primarily auditory person, it strengthened her skills in the areas you’re concerned about before sending her off to do by herself. Now she quietly reads beautifully on her own, with great narration.
Another idea is have him read Busy Times to himself out loud, too; then have him narrate. If he’s reading monotone, read to him as an example only to show him how to make the story more interesting through “storytelling” to himself, per say. I hope that makes sense. With these techniques, he’s not getting out of reading it, just in a different way.
HTH, RAchel