Some people called Michael S. Hart a Don Quixote, always tilting at windmills.

As it happens, Cervantes’s classic tale of the man of La Mancha is one of the more than 36,000 books in Project Gutenberg, a monumental free online library that Mr. Hart conceived of four decades ago, when the Internet was in its infancy and generations before the birth of iTunes and Wikipedia.

Mr. Hart, 64, was found dead Sept. 6 at his home in Urbana, Ill. He had a heart attack, said his brother, Bennett Hart.

A self-described “truck driver who got loose in academia,” Mr. Hart was a “legend” in the world of digital libraries, said Brewster Kahle, the founder of the online library Internet Archive.

Mr. Hart was credited with inventing the “eBook” in 1971. He often said he was just at the right place at the right time.

As a student at the University of Illinois, Mr. Hart was given access to a network-connected mainframe computer. He told USA Today that, by his estimation, the university had allowed him $100,000 worth of time on the machine, with the goal of improving his skills.

He was thinking about a way to repay the university. Then one evening, after Independence Day fireworks, he got hungry.

“I stopped at the grocery store to pick up a snack to take to the computer room, and they’d stuffed a copy of the Declaration of Independence on fake parchment in my bag,” he told USA Today in 1999. “I was pawing around to look for something, found it and decided, ‘If I put this up online, it will last a long time.’ ”

Mr. Hart manually typed in a copy of the Declaration of Independence and posted the document so that anyone on the network — about 100 people — could access it.

That single volume gradually turned into a massive library known as Project Gutenberg, named after the 15th-century inventor of the printing press. Over the following decades, Mr. Hart recruited hundreds of volunteers to help him manually type or scan in thousands of classics in the public domain, plus copyrighted works they had permission to reproduce, for the online library.

At times, Project Gutenberg drew criticism that it offered unreliable editions that were not always entirely accurate. For Mr. Hart, the project was simply about delivering as many books to as many people as he could.

“There are two things in the world that are truly, totally free with an endless supply,” he told the Chicago Tribune in 1999. “The air we breathe and the texts on Project Gutenberg.”

Michael Stern Hart was born March 8, 1947, in Tacoma, Wash., and grew up in Urbana. His parents worked as code-breakers during World War II; his father became a Shakespeare professor, and his mother a mathematician.

Among the first books Mr. Hart added to Project Gutenberg were the works of Shakespeare and the first 100,000 prime numbers.

Mr. Hart studied chemical engineering at the University of Illinois before dropping out because he did not like his classes. He was drafted into the Army during the Vietnam War. He subsequently returned to the university and graduated — in two years, with straights A’s — with a liberal arts degree, his brother said.

Survivors include his mother, Alice Woodby, and his brother, both of the Washington area.

Mr. Hart cobbled together a living with the money he earned as an adjunct professor and with grants and donations to Project Gutenberg. But he led a life of near poverty, Kahle said, and “basically lived off of cans of beans.”

Kahle and other friends recalled that Mr. Hart’s house in Urbana was stacked, floor to eye-height, with pillars of books.

The man who spent a lifetime digitizing literature lived amidst the hard copies, which he often sent home with visitors. It was one more way for him to share his books.