What's good and not so good about the conclusion to the first Wallander novel

Some good things and some not so good about the conclusion of Henning Mankell's first Wallander novel, Faceless Killers: on the plus side, Mankell deftly handles many complex plot elements, including two killings (murder of elderly farmer and his wife, revenge killing of a Somali asylum-seeker), and we never lose site of the connection between the two killings: the rumor that the farmer was killed by one of the newly arrived immigrants in Sweden spurred the revenge killing and other social outrages. Mankell also keeps us guessing toward the end and surprises us in the last two chapters as all the clues he's planted turn out to be false leads: we learn that it wasn't the farmer's son out of wedlock who'd done the killing nor in fact anyone who even knew the farmer and his wife. I expected a more simplistic ending and Mankell rose above that - a little. What's troubling about the ending is that he introduces all kids of new information in these last chapters: This is not a novel that a reader could possibly solved based on info in the first few chapters. In that sense, maybe it's more like a typical police procedural and less like typical crime fiction, but it's still somewhat dissatisfying (spoilers!): I mean OK he was killed by two guys who saw him make a big bank withdrawal and followed him home. Shouldn't that have come up much, much earlier? So much of this novel is dependent on ridiculously fortunate circumstances, e.g., a guy in the refugee camp who can ID cars by their engine sound, and most notably a bank teller w/ an extraordinary memory (it seems she could have solved the whole thing at page 50, but that where would we be?); I suspect she will play a role in later Wallander novels. We don't exactly expect crime fiction to be realistic, but I at least expect it to play by the rules: stay w/in the bounds of probability, don't introduce major plot elements at teh finish line, open up a little and let us know what the protagonist is thinking, not just what he's doing.