Make this sentence grammatically correct. My favorite, young adult, fiction novel is The Princess Diaries.

My favorite young adult fiction novel is "The Princess Diaries."

To make the sentence grammatically correct, remove the commas and capitalize "favorite" and "young adult":

"My favorite young adult fiction novel is The Princess Diaries."

To make the sentence grammatically correct, you should remove the unnecessary commas. Here's the corrected sentence: "My favorite young adult fiction novel is The Princess Diaries."