The twelve adventures in this hardback version string together beautifully to make a whole campaign. The story is excellent, the dungeons deadly and the villains really nasty.
The hardcover contains extra goodies that were not in the magazine versions.
For a start there is the extra adventure, Drakthar's Way, which although quite short does bridge the gap between chapters 1 and 3 very well. It also has some foreshadowing of future events to tease your players with and increase their sense of versimilitude.
Also new to the hardback are some beautiful NPC portraits. They have proved to be excellent character forming handouts for my players.
One big difference is that the hardcover is designed for six players as opposed to the magazines four.
There are many other extra things included as well, often just where you need them to be. Some are brand new, some are taken from the previous web supplements.
I dropped mine in the bath, it dried out okay and is perfectly readable and usable but it's such a sexy and well presented product that I felt bad enough about it to purchase a new one.
I definitely be buying the Age of Worms if it comes out in hardback. Although I have all the magazines it's much easier to carry a single book around!