Ds (4 1/2) loves the first Harry Potter film, & he's not a toughie by any means - terrified by Finding Nemo.
Haven't started reading it to him yet (currently knackered from work & reading easy stuff that dd1 will like too..) but we're looking forward to beginning it over Xmas.
It might turn out to be too long/boring - we gave up on 'The Lion, The Witch & The Wardrobe' - but I think there's no harm in trying it & possibly abandoning it, then coming back to it in a year or so.