What influenced Frank McCourt to write Angela's Ashes?

To fully understand Frank McCourt's life obsticles leading him to write Angela's Ashes, read the books in order - Angela's Ashes, 'Tis and Teacher Man.

Here's a book review on his Pulitzer Prize winning novel "Angela's Ashes":
http://optimistsheryl.blogspot.com/2010/01/first-book-review-of-2010-angelas-ashes.html