I have too much on my plate but I love this idea even if I'll never get to it.
There's an old witch with a powerful book of spells. She comes from a long line of witches guarding this book. She was supposed to recruit an apprentice who could be trusted with the power but every apprentice she had over her life failed her. She decides to destroy the book and the book doesn't like it.
The book is burning, lashing out, but nothing it can do can save itself. Even the spells she's read and has in her own head can't motivate her choking and old body to action.
A boy, our hero, plays the hero and rushes into the witch's burning house and carries her out to the curb. In the smoke and ashes, he inhales the last death throes of the spellbook allowing the magic to suffuse through him.
Without the spellbook to ritualize and control the spells they emit by his own thoughts and feelings, if he's a teenager those feelings are powerful over the top.
If I wrote this, it would be a harem story. There'd be a scorned apprentice MILF as the villain. Maybe even the hero's own mother. But I'm not going to write it. If it interests anyone, take it all or whatever bits you like.