Her book, 'The Woman I Was Born To Be,' will be published in the autumn and is already guaranteed bestseller.
Boyle said: "When I strutted on to the stage for that audition, I was a scared wee lassie, still grieving for my mother, not caring how I looked. I think I've grown up a lot in the last year, become more of a lady, and I'm not so frightened any more. I'm writing this book to try to show that you shouldn't judge a book by its cover and I hope it will benefit other people."
She went on: "My story demonstrates that you shouldn't just look at the label, you should look at the whole person, emotionally, physically, mentally and spiritually, and I hope that telling it will show that dreams are not impossible, if you've got courage and a willingness to go on no matter what the circumstances."
The Scottish singer, whose career has been guided by Simon Cowell, has also seen the downside of fame after struggling with the pressures of appearing in the public eye.
Her publisher Transworld said: "This astonishing transformation has not always been easy for Susan, faced with all the trappings of celebrity, but in the whirlwind of attention and expectation, she has always found calm and clarity in music. Susan was born to sing."