Here is an interview with Timothy Doner who taught himself 20 languages:
“During the past few years, I’ve been referred to in the media as “The World’s Youngest Hyperpolyglot” — a word that sounds like a rare illness. In a way it is: it describes someone who speaks a particularly large number of foreign languages, someone whose all-consuming passion for words and systems can lead them to spend many long hours alone with a grammar book.”
Definitely worth reading.
And don’t miss his TED talk: