Anne Karin Thorhus was born in Trondheim, by parents Rune Sanfrid Thorhus and Hjørdis Wedø. She is married to playwright Edvard Normann Rønning. She is cand.mag. from the University of Trondheim. She was the first female scuba diving instructor of the Norwegian Diving Federation (Norwegian: Norsk Dykkerforbund).
Kim Småge's first two crime novels, Nattdykk (1983) and Origo (1984) feature Anne-kin Halvorsen, a female diver, as the main character. She followed up with the thrillers Kainan (1986) and Lex Love (1991). She also wrote two youth's novels, Kainan in 1986, and Interrail in 1988. Kvinnens lange arm (1992) is a collection of crime short stories. The crime novels Sub Rosa (1993), En kjernesunn død (1995), Containerkvinnen (1997), Solefall (2002) and Dobbeltmann (2004) all feature the police detective Anne-kin Halvorsen as main character.
Småge was board member of the Norwegian Authors' Union from 1987 to 1991, and again from 2002 to 2004. She served as president of the society Skandinaviske Kriminelle Selskap in 2001.
She was awarded the Riverton Prize in 1984, and the Glass Key award (for best Scandinavian crime novel) for Sub Rosa in 1993. She has received the Palle Rosenkrantz Prize for best novel translated into Danish (for En kernesund død).