Mäki published his first novel Enkelipölyä in 1985. His most well-known character is private detective Jussi Vares who was first introduced in the novel Moukanpeli released in 1986. A total of 25 novels about Jussi Vares have been published to date (in addition to his other non-Vares books). All novels take place in the city of Turku. Eight of the Vares-novels have been made into feature films and a ninth is currently in production with a scheduled release in Januari 2015. Some films have been released in movie theaters and some straight-to-DVD.
Mäki is one of the most influential modern Finnish authors. His most recent novel Cowboy was released in 2014 and is the final book in a trilogy (the other two are Sheriffi and Intiaani).