The book; "Ghosts of Ascalon" is pretty engaging, to say the least. If you are a fan of ANET's Guild Wars you will gladly pick this book up which expands into the world of Guild Wars 2. As you follow the adventures of a group of unlucky people, the story will twist, turn and unfold itself into a beautiful (and familiar) setting.
This book cost me $7.99 at Borders. If you are cheap and want to save a few dollars, you can find them use on Amazon for about half the price, but with shipping, you're better off buying a new book.
I don't want to bore anyone reading this (Not like anyone does), so I will end it with a simple thing.
Buy the book if you enjoy reading the likes of 'Lord of the Rings' or 'Eragon'.
*EDIT*
As of this morning (August 8th, 2010) I just finished the last of the book. 370 pages total and cannot wait until the second book, "Edge of Destiny".