This book was more difficult for me to read than the previous Wallander books. It doesn't give anything away to say that he struggles with oncoming dementia (since it's revealed very quickly), and this was the last book that Mankell wrote about his detective. So, it's pretty darn sad - and whether it was because of my frame of mind while reading it, or the advent of the cold (which is what I always think of when I think of Sweden, even when it's hot there!), or remembering my grandmother and her journey through dementia - it was more difficult to pick up and keep going with this one than with his other novels.
And, yes, Mankell just died today. That feels like an extremely odd codicil to me, and is kind of freaking me out a bit.
Perhaps the other issue I had with the novel is that it moves extremely slowly (I think one review I read said that "there are many pages between deaths," ick, what a way to put it, even though it's a murder mystery). It's probably that slow because it's dealing with difficult themes (old age, death, the aforementioned dementia), and it needs many pages to delve into those themes. But it was one more reason I had trouble picking it up. Also, I wouldn't say I preferred the filmed version of it (from the Swedish TV series "Wallander") - they simply provide different avenues into the same themes.