Trained as a biologist in zoology and ethology at the Leiden University, he taught that subject before becoming a full-time writer in the 1980s, having made his debut as a novelist in 1971 under the name Martin Hart with Stenen voor een ransuil ("Stones for a Long-Eared Owl").

He is the author of many novels, including Het Woeden der Gehele Wereld and De kroongetuige.

The themes of his novels, which often have an autobiographical component, include: His writings are full of detailed descriptions of nature (e.g. the weather, insects, plants) and show his passionate love for classical music (especially the music of the composers Bach, Mozart and Schubert).

't Hart has also written non-fiction, including Ratten (1973), published in an English translation as Rats by Arnold Pomerans (London/New York: Allison and Busby, 1982).

This turned out to be a disagreeable experience about which he wrote a story, "Ongewenste zeereis", that appeared in 2004 in Granta under the title "Rats".