The Magic Book

The key turned easily in the lock. Hans entered, half frightened at what he was doing, and the first thing he beheld was a heap of bones.

That was not very cheerful; and he was just going out again when his eye fell on a shelf of books. Here was a good way of passing the time, he thought, for he was fond of reading, and he took one of the books from the shelf. It was all about magic, and told you how you could change yourself into anything in the world you liked.

Could anything be more exciting or more useful? So he put it in his pocket, and ran quickly away out of the mountain by a little door which had been left open.

The Magic Book, The Orange Fairy  Book, Andrew Lang