What other sort of book could Catullus be talking about here? I feel sure he is talking about a volume of Christmas carols.
Di magni, horribilem et sacrum libellum
Quem tu scilicet ad tuum Catullum
Misti, continuo ut die periret,
Saturnalibus, optimo dierum!
Great gods — what a horrible and damnable little book you sent your Catullus — so that on every day throughout the Saturnalia (the best of the holidays) he would perish of boredom.
Catullus (c. 84–c. 54 B.C.E.), Carmina XIV.
Catullus finishes the poem by threatening to visit a book dealer and send omnia colligam venena [every sort of noxious trash] to his friend.