Being an avid reader of webcomics, I've often wanted hard copies of them, so that I can read them while traveling (also works as show-off) and this book is exactly that - it doesn't contain all of them though, a few selections of the many first released on the site.
All of the strips can be read for free but this book doesn't fail to make me happy everytime I open it and see the quirky hand-drawn faces.
It delves into depths of science and love (often both at once, sometimes just sarcastically but sometimes serious). As an xkcd (the author's webcomic i.e) fan, you might tend to think that I'm biased but trust me even with that, this book was worth the money (costs even more here).
The book has all kinds of humor, nerd/geek and slapstick alike (also a few adult ones). I really like the mix, you know, with all it's seriousness and humor and simple laughable errors.
It's introduction blames the reader for making a poor economic choice, that is - buying the book when you can read it for free online. The book really has nothing more, other than a few coded footers (if you can decode them, they're quite interesting) and sometimes, little art (you know, just like that).
The book is not a good economic choice but it's a damn good memory (your game now).