A Fictional Confession: Amok Case

The chain of real events started on the 13th of November 2000, when Dariusz Janiszewski, an entrepreneur from Wrocław (a city in south-western Poland), left his office to meet with a customer and was never heard from again. Earlier that day, an anonymous client called and said he was interested in the services of Janiszewski’s advertising company, he requested to talk to Janiszewski alone. A month later, fishermen discovered the tied-up body of Dariusz Janiszweski in the Odra river. The case went cold for three years but in that time a new detective, Jacek Wroblewski,  uncovers a novel by Krystian Bala called Amok that detailed the heroic killing in the name of love. A question arises though, does one shelve this book in the fiction or nonfiction section?