Mackintosh's debut novel
I Let You Go, published in 2014, was a
Richard & Judy Book Club pick. It won
Theakston's Old Peculier Crime Novel of the Year Award in 2016, beating
J K Rowling writing as Robert Galbraith. In October 2016, the French translation of
I Let You Go (
Te Laisser Partir) won "best international novel" at the
Cognac Festival Prix du Polar awards. Her second novel,
I See You, was also a
Richard & Judy Book Club pick, winning the readers' vote. It charted at number 1 in
The Sunday Times original fiction list and was shortlisted for Crime & Thriller Book of the Year in the
British Book Awards. In March 2018 Mackintosh published her third novel,
Let Me Lie, which charted at number 1 in The Sunday Times original fiction list. It was also chosen as a
Richard & Judy Book Club pick. As of May 2019 her novels were published in more than 40 languages and had sold more than two million copies worldwide. Mackintosh's fourth novel,
After the End, was published in hardback in June 2019 and became an instant
Sunday Times bestseller. She then published three more
Sunday Times bestsellers:
Hostage,
The Last Party and
A Game of Lies. ==Other activities==