Well, I wouldn't suggest that you buy this book if you are unaquainted with Thompson's work, you should buy Fear and Loathing in Las Vegas, then, if you like that, buy The Great Shark Hunt. I say that because I have offered The Great Shark Hunt to people who haven't read any Thompson and they were put off by its sheer length and the content of some of the articles.
The reason I like this book is because it is pretty open-ended, because the book is a collection of articles you can read the ones that interest you and skip the ones that don't grab you. There is no reason why you should read it straight from cover-to-cover.
There is some pure gold in here, including excerpts from Fear and Loathing in Las Vegas, the infamous The Kentucky Derby is Decadent and Depraved (considered to be Thompson's first gonzo article) and many other gems.
I'd say, buy this, but only if you are sure you like Thompson because it isn't the best means of getting started on him. To sum it up in one line; If you love Hunter S. Thompson's work, you'll love this...