Growing up I LOVED the William books! Even my dad, who's not that much into fiction, has one cherished book in the series, which he got as a kid to cheer him up after breaking his leg skiing.
Of course these books would appeal to John. Besides what Norman mentions, they are absolutely hilariously funny! All those excuses! His mom says he's not allowed to play tigers and tiger tamers any more so of course he doesn't. He's a very obedient TO THE LETTER boy! He just play lions (or jaguars or gepards or any other wild animals) and tamers instead!
Oh man, this SO takes me back!