The Wee Free Men: The Beginning (Discworld, #30 & #32)

When Tiffany Aching sets out to become a witch, she faces ominous foes and gains unexpected allies. As she confronts the Queen of Fairies and battles an ancient, bodiless evil, she is aided (and most ably abetted) by the six-inch-high, fightin', stealin', drinkin' Wee Free Men. Laugh-out-loud humor and breathtaking action combine in the books that launched the unforgettable adventures of a determined young witch and her tiny but fierce blue friends.