Martin was now so old that for his birthday that year his father gave him a book without any pictures in it! Martin's father noticed his disappointment, and told him,

"Son, this isn't just any old book, it's a magic book. But to discover its magic you'll have to read it."

Well, that was better; Martin liked everything to do with magic. He started reading it, even though he wasn't overly enthusiastic. The next morning, his father asked him,

"Have you found the magic key?"

So... there was a key to find! Martin ran off and flicked through the book, but there was no sign of the key. He came back, very annoyed, but his father warned him,
"You won't find it like that. You have to read the book."
Martin didn't have much patience, and he stopped reading the book, thinking his father was trying to trick him into reading a bit more, just as Martin's teacher had suggested to his dad. A little later, his sister, Angela, who was just a bit younger than him, asked him for the book so she could try reading it. After several days of trying to read it without great success, she appeared in the lounge, happily screaming,

"I've found it! I've found the key of the magic book!" And she would not stop talking about all the worlds and places she had visited using that magic key.
All the talk ended up convincing Martin to resume reading the book. At first it was a pain; there wasn't even one miserable picture in the thing. But, gradually, the story started springing to life, and Martin got interested in the adventurous Prince's life. Then, suddenly, he was there.

The book itself was the key!

It was true that whenever he opened it, he felt transported to its valleys and seas, and he lived the adventures of its pirates, Princes, and wizards, as though they were himself. And his head and his dreams filled with adventures whenever they got a chance.
However, the best thing about that story was that from then on, in every new book, he saw a new key to a thousand worlds and adventures. Martin never stopped travelling and travelling on those letters and words.