There have been a few over the centuries, some of indisputable literary merit:

1. Ossian. In 1765, the Scottish poet James MacPherson published "The Works of Ossian", a collected series of epic poems he claimed to have translated from an ancient Gaelic poet, the said Ossian, who was quickly acclaimed by many to be comparable in terms of literary merit with Homer. Even Napoleon became a great fan. Problem is, MacPherson had written them all himself. Or..is it a problem? Good is good, isn't it?

2. Chatterton. In 1769, Thomas Chatterton, a poor attorney's apprentice, claimed to have discovered a chache of medieval manuscriopts in a church in Bristol written by a 15th c. monk, one Thomas Rowley. This "discovery" coincided conveniently with the current literary taste for "Gothic Revival" poetry and became a sensation. When the 17-year old Chatterton was unmasked as a hoaxer, he took poison. There's a famous painting of his sad death by Henry Wallis.

3. The Hitler diaries. Stern magazine swallowed this famous 1983 hoax hook, line & sinker.

4. Joseph Sickert. The entire Jack the Ripper/Royal baby/Masonic conspiracy/ Sir William Gull urban myth all started with Sickert, who conned a journalist on the local paper (Stephen Knight of the "East London Advertiser") into believing that his tall-tales were all true. Knight's subsequent book "Jack the Ripper: the Final Solution" is accepted by many as gospel to this day. One of the most successful literary hoaxes ever, this one will not lay down and die.

5. Lobsang Rampa aka Cyril Hoskins. His 1957 book "The Third Eye", concerning a young lad's apprenticeship in a monastery of Tibetan monks, was widely accepted for decades, gaining widespread popularity in the 1960's, that decade of interest in all things Eastern/spiritual. Astral travel, clairvoyance, telepathy...I must confess, with a blush, that I once bought into this account myself, as a young man. But I should have realised something fishy was going on when "Lobsang Rampa" (Cyril) gave his account of his "Third Eye" being opened by having a hole drilled in the middle of his forehead...

Not sure if you could call this a literary hoax, but I did read The Diary of Jack the Ripper. It was meant to have been written by James Maybrick (Ripper suspect). The original book (I have only seen the facsimile) was a leather bound original Victorian scrapbook with gold leaf bands on the spine. The writing and ink used were convincing and fooled many experts. It transpired that an unlikely couple Michael Barrett and Anne Graham from Liverpool cobbled the whole thing together.

Yes, and Barrett later produced- like a rabbit out of a hat- a pocket watch he claimed to have been owned by James Maybrick, conveniently inscribed with the initials of the Ripper victims.

The original "diary" was, indeed, written in a Victorian-era ledger, but the first 50 or pages had been mysteriously removed...

The Maybrick hoax was actually quite ingenious because the dates matched and Maybrick was an arsenic-eater (the speed-freak of the Victorian era), the infidelity of his wife Florence providing a convenient "motive" for Maybrick to embark on the Ripper killings.

All hokum, though.