Lefferts' name or her distinctive "W.E.L." signature appears on many book jackets, including the U.S. edition of W. Somerset Maugham's The Casuarina Tree (1926), DuBose Heyward's Angel (1926) and M. P. Shiel's Dr. Krasinski's Secret (1929).
Among his friends and acquaintances were the writers Yone Noguchi, Arthur Ransome, M. P. Shiel, and the artist Pamela Colman Smith.
Tartarus publishes classic supernatural fiction by Arthur Machen, M. P. Shiel, Hugh Walpole, Gustav Meyrink, Oliver Onions, and more modern authors such as Sarban, Robert Aickman and David Lindsay, alongside contemporary writers including Quentin S. Crisp, Mark Valentine, Angela Slatter and Rhys Hughes.