Firewall is the 9th book in the Wallander series, chronologically.

It’s good.

A series of bizarre incidents sweep across Sweden: a man dies in front of an ATM, two young women slaughter an elderly taxi driver, a murder is committed aboard a Baltic Sea ferry, and a sub-station engineer makes a gruesome discovery while investigating the cause of a nationwide power cut. As Wallander investigates, he uncovers a sinister plan …

The major background theme around which the action takes place is the dilemma of the Western economic system versus poverty. …

Wikipedia