Okay, the Young Adult Literature genre is pretty easy to tag in this book.
Main character is young. Check. Parents are maybe not as involved as you'd think. Check. First person narrator. Check. Pretty much your classic YA.
By comedy, we're not talking stand-up comedy or anything. Because of Winn-Dixie isn't a laugh-out-loud funny book, except maybe occasionally when Winn-Dixie gets up to his old tricks.
Instead, it's cheerful. Sure, Opal goes through some rough times, but she's always got a good attitude and spins events positively. It helps that she's got a sneezing, laughing dog as a happy-go-lucky sidekick. Oh, yeah, and there's even a happy ending. Opal's mom doesn't come back—it's not that kind of ending—but she and her dad learn to cope and reconnect.
We admit we're stretching a bit here. Opal is 10 when the story takes place, and she's 11 as she tells it. So she's not really transitioning into adulthood or anything. But she is transitioning from childhood to adolescence, and we can tell by the way she learns to cope with her mom's abandonment.
At the beginning of the story, she knows nothing about her mother and aches for her, and by the end, she has come to terms with her mother's absence and rotten choices. At that point, she still loves and misses her, but she can move on and get past it.
So, we're not talking bill-paying, 9-5 job-working adulthood here, but we've got to give Opal props for maturation. And thus, we bestow upon her the coming-of-age genre. Consider yourself knighted, Lady Opal.