As a TA with over twenty years in primary schools, provided he CAN read for for his age, or beyond, I don't think you should worry too much.
What is he like at writing? Can he write simple stories, or recounts of outings? And what about all the other subjects, particularly Numeracy, and PE and games activities, is he happy with them?
Children's 'likes' and 'dislikes' do come and go quickly sometimes, for no apparent reason that adults can see, though the child probably has his own reasons.
A BRILLIANT book, by Anne Fine, "Diary of a Killer Cat", has plenty of scope for 'acting' and is hilariously funny, with a subtle 'twist' (which may need to be explained to a 6 yr old) but I should think he might enjoy it.
Is he on to 'chapter' books yet, as I wouldn't have thought he would get through one of those every evening?