Lancelot is a 1977 novel

Novel

A novel is a book of long narrative in literary prose. The genre has historical roots both in the fields of the medieval and early modern romance and in the tradition of the novella. The latter supplied the present generic term in the late 18th century....

 by the American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 author Walker Percy

Walker Percy

Walker Percy was an American Southern author whose interests included philosophy and semiotics. Percy is best known for his philosophical novels set in and around New Orleans, Louisiana, the first of which, The Moviegoer, won the National Book Award for Fiction in 1962...

. It tells the story of the dejected lawyer Lancelot Lamar, who murders his wife after discovering that he is not the father of her youngest daughter. He ends up in a mental institution, where his story is told through his reflections on his disturbing past. The novel compares the protagonist unfavorably to his namesake, Sir Lancelot

Lancelot

Sir Lancelot du Lac is one of the Knights of the Round Table in the Arthurian legend. He is the most trusted of King Arthur's knights and plays a part in many of Arthur's victories...

, as he experiences a vision of an empty modern American culture which invokes the symbolism of the mythical Wasteland

Wasteland (mythology)

The Wasteland is a Celtic motif that ties the barrenness of a land with a curse that must be lifted by a hero. It occurs in Irish mythology and French Grail romances, and hints of it may be found in the Welsh Mabinogion....

. Lamar's quest to expose this moral emptiness is a transposition of the quest for the Holy Grail

Holy Grail

The Holy Grail is a sacred object figuring in literature and certain Christian traditions, most often identified with the dish, plate, or cup used by Jesus at the Last Supper and said to possess miraculous powers...

; as he witnesses and records the increasing moral depravity of his wife and daughter during the filming of a Hollywood movie, he becomes obsessed with and corrupted by the immorality he seeks to condemn. The novel is replete with Arthurian references, including characters based on Merlin

Merlin

Merlin is a legendary figure best known as the wizard featured in the Arthurian legend. The standard depiction of the character first appears in Geoffrey of Monmouth's Historia Regum Britanniae, written c. 1136, and is based on an amalgamation of previous historical and legendary figures...

 and Percival

Percival

Percival or Perceval is one of King Arthur's legendary Knights of the Round Table. In Welsh literature his story is allotted to the historical Peredur...

.

Cultural references

During the second season of Lost, in the episode "Maternity Leave", James "Sawyer" Ford is seen reading a copy of the novel.
During the sixth season of Lost, in the episode "Recon", a copy of the novel is stacked with A Wrinkle in Time

A Wrinkle in Time

A Wrinkle in Time is a science fantasy novel by Madeleine L'Engle, first published in 1962. The story revolves around a young girl whose father, a government scientist, has gone missing after working on a mysterious project called a tesseract. The book won a Newbery Medal, Sequoyah Book Award, and...

 and Watership Down

Watership Down

Watership Down is a classic heroic fantasy novel, written by English author Richard Adams, about a small group of rabbits. Although the animals in the story live in their natural environment, they are anthropomorphised, possessing their own culture, language , proverbs, poetry, and mythology...

on the James "Sawyer" Ford's dresser in his alternate time-line.