Nick Hornby is the author of good books, including High Fidelity (which they made a movie of) and About a Boy (which they also made a movie of). His books are great for a wide audience, but this is his first written intentionally for teens.
Sam, the main character and narrator, is a regular sort of kid living a regular life in England. Except that his mom was a teenage mom, and now he's about to become a teenage dad at the age of 16. Yep, he knows about safe sex, but he made a mistake and now he is going to have to live out the consequences.
What makes this book such a good read is the realism of the situation - all of the characters are interesting people, but they are all human - even Sam - they make mistakes, say stupid things, do mean things, are awesome, are funny, are boring. And the other thing is being able to see the story of teenage pregnancy from the guy's point of view. Especially such an average, run of the mill guy like Sam.