Terry Pratchett's Tiffany Aching series, 'Wee Free Men', 'A Hat Full Of Sky', 'Wintersmith' and ' I Shall Wear Midnight'.
It's an original coming-of-age fantasy story set on the chalk hills in Terry Pratchett's Discworld. The series gets better with each book, and I felt by the time I had read the last that I wished they had been written when I was entering my teens. Tiffany is a character that really grows on you, and her learning of the craft of witching is clever and sometimes even profound. There is humour and wisdom and the joyous inclusion of the daft yet deeply loyal, Wee Free Men.
A series I haven't read, but it is on my wish list is 'Diary Of A Wimpy Kid' by Jeff Kinney. There are 8 books in the series so far.
In interview (wimpykid.com) the author said, "I wanted to write a story about the funny parts of growing up and none of the serious parts. I had a pretty ordinary childhood, but lots of humorous stuff happened along the way. So, I decided to write a book about what it was really like to be a kid, or at least what it was like for me."