Clazza, what if you look at a book about animals with him and you ask him to pretend to be the animals? Like doing a funny penguin walk with him, and sniffing around like a puppy, would he be more inclined to join in? Or has he got a specific thing he likes, eg, tractors, trains, and just pick one thing that he likes and targets that to get him interested? Or would he rather be pushing buttons to get some sounds from a book?
If he likes food, give him a snack and then read while he enjoys it. Would it help?