The Hobbit is a very good introduction to the fantasy books of Tolkien. The characters of his major work The Lord of the Rings are introduced, but the story is not so complicated.
I read this book for the first time when I was 10 years old, and later reread The Hobbit many times, discovering each time new details. Tolkien is sketching his world with colorful words, but without too many descriptions. You can imagine it very well, that is the real magic of this book.