My absolute favorite book from childhood was J.R.R. Tolkien's The Hobbit. It had all the things that children like in a good story: high flying adventure, colorful characters, goblins, ghouls, and a great big dragon. Bilbo's journey from the Shire to the Lonely Mountain has been a treasured literary classic for decades, and for very good reason.
Reading and rereading the book throughout my childhood, I almost felt like I was on the adventure myself; like Bilbo, Thorin, and his loyal band of dwarves were old friends who would take me along for the ride as many times as I wanted. The world Tolkien created instilled in me a love of books and a desire to read more, and explore all the other worlds that other authors had created. That to me is one of the greatest achievements of literature.