The Perks of Reincarnating as a Minor Character

When I died and reincarnated inside my favorite book, I felt like I won life's lottery. Now, it's clear to me that my purpose in existence is to protect my favorite characters, give them better lives, and save them from dying! I swear, in the name of all potterheads in the world, that I will stop this series from turning into a tragedy! (And have a freaking blast while at it!)