I think Toole was the most gifted novelist in English in the twentieth century, miles ahead of Hemingway and Fitzgerald and Joyce or anyone else. He was somewhat pretentious, and took his book to Simon and Schuster, the premier publisher at the time, thinking it worthy of no less.
He was put under the editorship of a man called Gottlieb, who admitted Toole was very talented, even more talented than Gottlieb, but there was a problem. Two of the characters, Gus Levy and Mrs. Levy (whose first name is never disclosed), were less-than-reverential, even satirical representations of Mr. Gottlieb's tribe. So he tried to persuade Toole to remove the characters, but Toole thought they were important. He was dangled along for a while, and began having trouble with his mental state. It is not outside the realm of possibility that he was poisoned or influenced in some covert way, he was that talented, rather like Edgar Allan Poe. They even pulled a villainous move, they gave Toole's plot to another writer who published a novel that effectively prevented the book from being accepted elsewhere. If you want the story of this, look up the book The Butterfly in the Typewriter.
He eventually committed suicide, and his mother, an eccentric grande dame with disappointed artistic ambitions, sent the manuscript to publisher after publisher, only to have it returned. Eventually she went to the office of Walker Percy at Louisiana State University, and demanded that he read it. He was completely overwhelmed, and when it was finally published under the august auspices of Louisiana State University Press, it won the Pulitzer.
It's sad to think what we lost, and then think how many times has something like this happened? Another example is Sixto Rodriguez, who made a great record in 1970, and someone pulled the plug on distribution, they buried it. It was smuggled out to South Africa, where it became a hit, unbeknownst to the world as the apartheid regime was pretty severe about information getting out. Finally, that too got out; some people think it was buried because Rodriguez was of Hispanic origin, but I think they didn't want competition for Dylan, or they didn't want someone of Dylan's status who would be unpredictable. It's hard to imagine why they shut it down. There's a good documentary on him called Searching for Sugar Man.
This is a documentary on Toole on Youtube, but when I post it here it says "playback on other websites has been disabled," something I've never seen before.