There are some Batman books that may not be age-appropriate, like some stories the short fiction collection "The Further Adventures of Batman", so taking into account that it's for a young boy... there were novelizations of episodes from the 90s animated series, written by Geary Gravel, those were aimed at young readers. "Dual to the Death" was an adaptation of the Two Face episodes.
There was also a novelization of the "Rise of Sin Tzu" video game, based on the same animated series. I think Devin Grayson, who wrote for Batman comics at the time, co-wrote that.
For a more humorous Batman like the shows you mentioned, maybe Alan Grant's novelization of "Batman & Robin" would work well. Maybe better than the actual movie, as you might actually imagine the old Adam West show cast as the characters.
Mind you, all of those you'd probably have to get second hand, as they've all been out of print for some time. There's also been quite a few young readers books based on Batman and Superman released in the last decade, but in my experience they relied heavily on pictures.