Ann Swinfen's first three novels, The Anniversary, The Travellers, and A Running Tide, all with a contemporary setting but also an historical resonance, were published by Random House, with translations into Dutch and German. The Testament of Mariam marked something of a departure. Set in the first century, it recounts, from an unusual perspective, one of the most famous and yet ambiguous stories in human history. At the same time it explores life under a foreign occupying force, in lands still torn by conflict to this day. Her second historical novel, Flood, first in the Fenland Series, based on true events, takes place in East Anglia during the seventeenth century, where the local people fight desperately to save their land from greedy and unscrupulous speculators. The second novel in the Fenland series, Betrayal, is set partly in East Anglia and partly in London. This Rough Ocean is a novel based on the real-life experiences of the Swinfen family during the 1640s, at the time of the English Civil War.

Currently she is also working on a late sixteenth century series, featuring a young Marrano physician who is recruited as a code-breaker and spy in Walsingham's secret service. The first book in the series is The Secret World of Christoval Alvarez, the second is The Enterprise of England, the third is The Portuguese Affair, the fourth is Bartholomew Fair and the fifth is Suffer the Little Children. A sixth novel in the series is due in 2015.