Eats, Shoots & Leaves by Lynne Truss that is a grammarian with quite a sense of humor. The book is both informative and funny as it discusses various points of grammar and of style.
The book covers different points of grammar, focusing on punctuation and its use. She grabs examples from her surroundings and compares the actual stated with the intended meanings.
Although she uses the British style, she often notes differences between American and British English, then pokes fun at everyone. Any ready will find a thoroughly enjoyable read and will learn a few points of grammar in spite if himself.