David T. Lee (Sci-fi)
David T. Lee wrote a sci-fi at age 7 (4,500 words), published his 5-book series by age 12.
The Adventures of Danny Hoopenbiller series:
Book 1: Danny and the Portal of the World (4,500 words at age 7).
Book 2: Danny and the Trip to Outer Space (6,500 words at age 8).
Book 3: Danny and the Invasion of the Dinosaurs (17,000 words at age 9).
Book 4: Danny and the Revenge of the Dinosaurs (20,000 words at age 10).
Book 5: Danny and the Wrath of the Dinosaurs (18,000 words at age 12).