Continuing on the subject of punctuation, I do not think there is a better book than Eats, Shoots and Leaves by Lynne Truss. The blurb on the book says it all: "The Zero Tolerance Approach to Punctuation!".
Unlike other books on Grammar, this one is wickedly humourous. It has been on various best seller lists, so you may already possess a copy. If you want to know more, you may want to read a review on Eats, Shoots and Leaves on my Squidoo lens. Enjoy!