She published under the name Françoise Mallet to avoid embarrassing her family, due to the novel's scandalous (lesbian) content.

[2] Le rempart des Béguines was translated and published in America as The Illusionist and later on it was reprinted under the titles Into the Labyrinth and The Loving and the Daring.

It is set in a town that resembles Mallet-Joris' native Antwerp and addresses the themes of social class and lesbianism.

[4] She followed her first work with a sequel in 1955 named La chambre rouge, in English; The Red Room.

In it, she focused less on lesbian themes but continued her treatment of social class and norms in Belgium.

[5] Mallet-Joris' novels frequently deal with interpersonal relationships and social class in France and Belgium.

She has also written works of non-fiction, like The Uncompromising Heart: A Life of Marie Mancini, Louis XIV's First Love in 1964, and she has written essays about her philosophy of life and writing in Lettre à moi-même (A Letter to Myself) in 1963 and La Maison de papier (The Paper House) in 1970.

Lilar won the "Librarians' Prize" (Prix des bibliothécaires) in 1958 for House of Lies (in French, the title was Les mensonges which means simply "Lies"), the Femina Prize in 1958 for Café Céleste (in French, it was called L'empire céleste which means "Heavenly Empire" or "Celestial Empire", a title that is highly ironic) and the Monaco Prize in 1964 for her biography of Marie Mancini.

Around 1970, Lilar met Marie-Paule Belle, a French variety singer who was openly lesbian.