This book really is Lone Wolf at its best. It has all the hallmarks which make the series so special - a varied, well-depicted and intriguing setting, an interesting scenario with plot twists (things stop going to plan in section 1!), a range of newly-created monsters and villains, and an epic showdown bringing the series back to its starting-point - the war with the Darklords.
The (vaguely Arabesque) desert setting of Vassagonia is divided into a range of varied landscapes through which the player travels, ranging from the massive city sewer system to the opulent royal palace and the desert wilderness itself, and featuring such unusual settings as the interior of a volcano and the king's private botanical garden. As in several other books, the environment is entirely hostile - Lone Wolf is running or hiding from adversaries for most of the duration. There are many items to find - some with unexpected uses. And it is not at all predictable - the eventual goal of the quest is not that mentioned in the introduction, and only appears at all halfway through.
On the monsters and NPCs, expect a vicious secret police/assassin force, undead warriors mounted on giant birds, a flying ship manned by dwarfs... not to mention such nasty traps as disease-inducing rusty armour and biting spiders hiding in handy escape-routes.
A word of warning though - the book should be read as part of the series; I would imagine it is very difficult played as a solo adventure, with 3 fewer Kai disciplines and no Sommerswerd.