See also: Librivox [1], for public-domain audio books read by actual humans
The sibling poster is right, the quality varies. But the upper end of the quality range is really quite good. One of the best-read audiobooks I've ever heard was a Lit2Go edition of Pygmalion. And, for that matter, one of the worst-read audiobooks I've ever heard was an edition of an extremely famous and commercially successful book that I bought on Audible.
Sorry, just joking. But here's a reason: these things were not quality-checked at all. Click on Moon Voyage by Jules Verne and be greeted with a very human-like voice reading an numbered list of "other works by the author" in an extremely awkward fashion that's probably caused by how the .TXT file is organized.
EDIT: The first book on the list https://marhamilresearch4.blob.core.windows.net/gutenberg-pu... is "100%: the Story of a Patriot" and the LibriVox version is at https://librivox.org/100-the-story-of-a-patriot-by-upton-sin...
Amateur readers are hit & miss. A lot of professional readers are actors or have a lot of experience. There is a reason people do pay for professionally read books instead of electronic reading or librivox only.