Of all the punctuation marks, the lowly comma may be the most misunderstood and most misused. Some writers use too many, some not enough, and some just place them in the wrong place. 

This book will help. It explains where to use commas and how to use them, and in many cases even why to use them. It also explains when you can break the so-called rules and use commas the way you want. Best of all, it does all this without resorting to complex grammatical terms. Everything is explained in plain English.