Here are five of the youngest novel writers in the USA:

Alec Greven: Alec wrote his first book, "How to Talk to Girls," at the age of 9.

This book became a New York Times Bestseller, and he has since published several other titles, including "How to Talk to Moms" and "How to Talk to Dads"  

Christopher Paolini: Christopher wrote "Eragon,"

The first book in his Inheritance Cycle series, at 15 and it was published when he was 18. His series became a bestseller, making him one of the youngest authors to achieve such success

Mattie J.T. Stepanek:

Mattie started writing poetry at a very young age and published his first book, "Heartsongs," when he was 11. He wrote several more books before passing away at the age of 13. His work touched many lives and he is remembered as a young poet and peacemaker​ 

Jake Marcionette

Jake wrote his debut novel "Just Jake" at the age of 12, which was published by Grosset & Dunlap. His humorous approach to middle school life earned him a spot on the New York Times Bestseller list

Nancy Yi Fan:

Nancy wrote her first novel, "Swordbird," at the age of 12. The fantasy novel, published by HarperCollins, became a New York Times Bestseller. She has since written several sequels and continues to be an inspiration for young writers