Fearless is a sort of picture book/chapter book hybrid tie-in to the SpongeBob Squarepants television show. Despite not being based on any episode I'm aware of (though I haven't watched the show in several years, I'll admit), it reads just like one. Unlike most SpongeBob tie-ins I've read, including those that are adaptations of episodes, everyone's refreshingly in character and maintains the show's style of humor and story structure without throwing it all aside to teach a cliche moral.
If you're looking for a SpongeBob tie-in, Fearless is by far the best I've seen yet.