"Stanley Unwin [chairman of publishers Allen & Unwin] believed that the best judges of children's books were children, so he handed [the manuscript of] The Hobbit to his ten-year-old son Rayner, who read it and wrote this report:
Bilbo Baggins was a hobbit who lived in his hobbit-hole and never went for adventures, at last Gandalf the wizard and his dwarves perswaded him to go. He had a very exciting time fighting goblins and wargs, at last they got to the lonley mountain; Smaug, the dragon who gawreds it is killed and after a terrific battle with the goblins he returns home - rich! This book, with the help of maps, does not need any illustrations it is good and should appeal to all children between the ages of 5 and 9.
The boy earned a shilling for his report, and the book was accepted for publication."
And thereby hangs a tale in more ways than one, as you'll see if you read the excellent J. R. R. Tolkien: A Biography by Humphrey Carpenter from which that passage comes.