^^^^ Girls love it too. Peter dozes off by the walls of a Norman castle and wakes to find a gauntlet in his hand...men in strange garb ride up and call him by name. Now read on.....
I had this as a Sunday School prizes, have read it and read it to youngsters and my grandchildren are now enjoying it. You can find it on Amazon.
Other very strong recommendation is 'The Phantom Tollbooth' Milos..... somebody. Again daughters have passed it on to their children. A perfect duo.
Why not start with the first Narnia book, "The Lion, the Witch and the Wardrobe"
I was about 8 when I read it for the first time and it has everything that all kids love. I can't recommend it highly enough, and if he likes it, then there are lots of sequels that will last him until he is 10 !