I'm now going to make a broad statement: Mankell's Wallander books form the best detective series that has ever been written. Ever. Michael Ondatje seems to concur, which is just lovely.
Firewall is the 8th full-length novel in the series, and also the last. In the next novel, Wallander retires and we follow the exploits of his daughter Linda, who has also joined the police force. Knowing it was the last was a great shame, because it is also, probably, the very best of this incredibly, astoundingly fine series. At the close of each chapter sadness broke over me like a wave. Wallander may not be the most cheerful company, but he is charming and the most endearing of current detective. Mankell's style is also part of the reason why every single sentence is so spellbinding. I can't say why, I don't know exactly what it is about the way he writes that is so special, but nor do I want to. Like seeing how a magician performs his tricks, that may spoil it a little.
Part of the reason why it's all so engrossing is Mankell's mixture of details. Indeed, he depicts a level of procedural detail that should be all rights be dull, but is instead riveting. The reasons for this a re two: Mankell's superb prose, and the very real impression he has created through the entire series that the crucial breakthrough, the information which might crack the case wide open, could come from absolutely anywhere, from the most mundane of tasks.
Also, it may be true that Wallander is somewhat the stereotypical loner (although like them all he has things about him which make him truly original), the police-force background is not at all stereotypical. Unlike many series where the cop seems to constantly go it alone, Mankell creates a unique sense of teamwork, that I don't think I've ever come across before. There's a warmth in the team which surrounds Wallander, and the way they work together. He doesn't have a particularly antagonistic boss, or any colleague he particularly dislikes. They all play their part, they all play their role in a cohesive policing team, and it's a joy to watch it as it works. Mankell knows that otherwise his series may be just TOO bleak and depressing, so the team exists in a happy unity which is far more realistic.
As you may have guessed, I adore this series. Wallander is a superb protagonist, and while just now I said he was the stereotypical loner, in all honesty he isn't. He's actually completely different to his counterparts Bosch and Rebus, etc. Instead of being the attractive loner, he is REAL, he is HUMAN. He gets angry properly (rather than Rebus would), like a child - in Firewall his frustration becomes such that he snaps and throws a chair across a colleague's office. There isn't a single investigator like him.
Do yourself a favour - read this series. Don't start here (Faceless Killers is the first). It isn't for everybody, but serious fans of crime fiction cannot afford to pass it by.