Wikipedia describes the book thusly:
The Songs of Bilitis /bɪ’li:tis/ (Les Chansons de Bilitis; Paris, 1894) is a collection of erotic poetry by Pierre Louÿs (1870-1925).
The book's sensual poems are in the manner of Sappho; the introduction claims they were found on the walls of a tomb in Cyprus, written by a woman of Ancient Greece called Bilitis, a courtesan and contemporary of Sappho, to whose 'life' Louÿs dedicated a small section of his book. On publication, the volume deceived even the most expert of scholars. Though the poems were actually clever fabulations, authored by Louÿs himself, they are still considered important literature.
Louÿs claimed the 143 prose poems, excluding 3 epitaphs, were entirely the work of this ancient poet—a place where she poured both her most intimate thoughts and most public actions, from childhood innocence in Pamphylia to the loneliness and chagrin of her later years. Although for the most part The Songs of Bilitis is original work, many of the poems in the collection were reworked epigrams from the Palatine Anthology, and Louÿs even borrowed some verses from Sappho herself. The poems themselves are a blend of mellow sensuality and polished style in the manner of the Parnassian school, but underneath run subtle Gallic undertones which Louÿs could never escape. To give authenticity to the forgery, Louÿs listed some poems as "untranslated" in the index; he even craftily fabricated an entire section of his book called "The Life of Bilitis", crediting a certain fictional archaeologist Herr G. Heim ("Lord S. Ecret") as the discoverer of Bilitis' tomb. And though Louÿs displayed great knowledge of ancient Greek culture, ranging from children's games in "Tortie Tortue" to application of scents in "Perfumes", the poems were eventually exposed as a literary fraud. This did little to taint their literary value in the eyes of the readers, however, and Louÿs' open and sympathetic celebration of lesbian sexuality earned him sensation and historic significance.