(?) after the title means I'm not sure if it's a real publication/book.
Literature mentioned in Gaudy Night, by Dorothy L. Sayers.
There were so many authors mentioned in this book that I didn't jot them down and have only included actual titles. I listened to an audio version of the book and the titles were gleaned after the fact from my print copy by scanning for italicised phrases. Therefore I may have missed some and this is by no means a definitive list.
The Aeneid (by Virgil)
Alice in Wonderland by Lewis Carroll
The Anatomy of Melancholy (by Robert Burton)
Brave New World (by Aldous Huxley)
"A Chaucer Folio"
"Kai Lung" (by Ernest Bramah) - no particular title is mentioned
"Three Kelmscott Morrises"
The Man of Property (volume 1 of The Forsyte Saga by John Galsworthy)
Religio Medici (The Religion of a Doctor) by Sir Thomas Browne
The Search by C.P. Snow
"A Shakespeare First Quarto"
The Daily Trumpet (?)
The Daily Headline (?)
The Morning Star
There were so many imaginary books mentioned that I couldn't help including them.
I owe my thanks to The Invisible Library for most of this list:
By Harriet Vane:
Death 'twixt Wind and Water (work in progress)
Sands of Crime
A Study of Sheridan Le Fanu (proposed work)
Ariadne Adams by unknown
Dusk and Shiver by unknown
Modern Verse-Forms by Mr. Elkbottom (this was not in in the Invisible Library list, but I couldn‘t find any proof of its existence, so on the list it went)
Gas-Filled Bulbs by Jacqueline Squills
History of Prosody by Mrs. Lydgate (work in progress)
Jocund Day by unknown
Mock-Turtle by Tasker Hepplewater
Passion-Flower Pie by Mrs. Snell-Wilmington
The Position of Women in the Modern State by Mrs. Barton
Primrose Dalliance by unknown
Serpent's Fang by unknown
The Squeezed Lemon by unknown