Marianne Koester trained as a designer and a primary and lower secondary teacher. Her debut novel Leo lyver was published in 1981. Like almost all her books, it is written together with the writer and journalist Kjeld Koplev. Together they won the Borgens children's book prize in 1983 with the novel Stenørkenen. This was followed by Tyskerdrengen, 1984, which describes the conflict between two Danish-German boys and Danish children during the occupation. In her Bildungsromans Slyngveninder, 1985, Stjernepigen, 1986, and Drengetøsen, 1987, aspects of a modern girl's life are described.
Marianne Koester has also written books about China, such as Smertesommeren. En beretning fra Kina (N), 1990, and the text-book Kinesiske akrobatbørn, 1991. Her novel Rå is from 1993.
Additions by the editorial team 2011:
The above biography was first published in 1998. Since then, Marianne Koester has written a number of children’s and teenage books.