Nigel is a pretty average English teenage...vampire. His "parents" turned him many years ago, and existence is just not that great. He goes to school, but doesn't fit in. At home, he's the only one who doesn't have super speed or strength.
The Chloe appears--a new student at his school and all of a sudden, life is worth living. She is his reason for being--not that she would ever know. When she does realize he exists, it's mostly because he tells her he's a vampire. Family dynamics aside, Nigel is definitely learning how to be a vampire at the tender age of 100.
Told completely in journal entries, you get what the title promises. Each day is filled with more of the same...Nigel not fitting in and not having a clue. You might put the book down before you get to any of the interesting stuff, which is about 2/3 of the way in. I heard this compared to Diary of a Wimpy Kid. I've never read it, so I couldn't say for certain.