The Book of Staying in The Pit
Other mentioned books are things like "The Book of Going Forth", "The Book of Going Forth Around Elevenish" (which is attributed to a rather lazy Llamaic sect). These emphasize that the spiritual journey to enlightenment begins in the (metaphorical) morning, even if it is around elevenish.
In Britain, a demotic metaphor for "bed" is "pit". This book might therefore be to spiritual enlightenment what Rincewind is to heroism - an anti-text that advocates "sod enlightenment, have a long lie-in", which would be the ultimate extension of the logic of this escalating joke in Pyramids