His most famous books are The Pink and the Black, Homosexuals in France since 1968 (1996), Mainstream (2010) and In the Closet of the Vatican (2019), a New York Times bestseller.

Based on testimony by 41 cardinals, 52 bishops, 45 nuncios and ambassadors and hundreds of priests,[3][4] the book suggests that a large majority of priests and bishops in the Vatican, including those who make the most homophobic and traditional speeches about morality, are homosexuals, practicing or not.

[5][6][7] "The Corruption of the Vatican’s Gay Elite Has Been Exposed" wrote, in a long piece for The Atlantic, Andrew Sullivan.

[8] The book was praised by Colm Tóibín,[9] the former head of Dominicans order Timothy Radcliffe,[10] the British historian Sir Diarmaid MacCulloch[11] and dozens of scholars and specialists.

[12] Martel wrote, or currently writes, for numerous publications in France and elsewhere (including Magazine Littéraire, L'Express, Le Point, Le Monde, Dissent, The Nation, Haaretz and Slate) and produces its own radio show, "Soft Power", a weekly live talk show on the entertainment, the medias and "the internets" for the French national public radio station France Culture (Radio France).