Ozzy Osbourne's son JACK has signed a lucrative publishing deal to pen his autobiography, despite being just 20 years old. The book, to be titled 21 YEARS GONE, will chronicle the reality TV star's descent into drug addiction and the pressures of parental fame. Jack's mother SHARON's lifestory Extreme last year (05) became Britain's best-selling hardback autobiography of all time, and now Jack has teamed up with publishers Pan MACMillan to emulate her success.