She became a student at MH secondary school, trained as a secretary in England and later finished a BA degree in pedagogy and education at Háskóli Íslands, the University of Iceland.
The novel was shortlisted for the CWA International Dagger, a prestigious award from the British Crime Writers' Association, and was hitting bestseller lists worldwide.
It told a story of the aid worker Úrsula returning to Iceland for a new job in the government, and becoming drawn into the dangerous worlds of politics, corruption and misogyny.
Lilja has deep empathy for her memorable characters, as she takes on various social issues, and classic Icelandic themes to combine them with modern outlook, in the society evolving post financial crisis 2008.
Translators from Icelandic into the many languages include: Ursula Giger, Angela Schamberger, Anika Wolff, Tina Flecken (German), Quentin Bates (English), Jean-Christophe Salaün (French), Tone Myklebost (Norwegian), Lucie Korecká (Czech), Aya Ashraf (Arabic), Nanna Kalkar (Danish), Sara Lindberg Gombrii (Swedish), Jacek Godek (Polish) and Liviu Szoke (Romanian).
Film rights to the Reykjavík Noir trilogy (Snare, Trap and Cage) have been sold to 66 Degrees North / Palomar Pictures International, based in California, US.
Lilja lives by lake Elliðavatn with her partner and a dog on the outskirts of the Icelandic capital Reykjavík but spends a considerable amount of time in Scotland.