What is the longest book ever written?

"Remembrance of Things Past" (or "In Search of Lost Time") by Marcel Proust is considered to be the longest novel ever published. Originally written in French, it consists of seven volumes and over 1,200,000 words. The novel is known for its introspective style, exploration of memory and time, and portrayal of French high society in the late 19th and early 20th centuries. It is widely regarded as one of the greatest works of literature in French literature and world literature as a whole.