Potentially, there are ~13,000 e-novels in MrDouble's collection - basically OCR'd vintage adult paperbacks. That's a staggering collection of smut by any standard. Most appear to be full-length novels - not short stories or quickies or similar things that you might find on ASSTR. At least for the novels I checked, the formatting was quite good - certainly nothing to detract from the reading.
The biggest 'problem' is the lack of an index. If a user opens any particular e-novel, there's a set of numbers (links) at the top of the page. You can 'click through' novel after novel using these links. You can make large 'jumps' by entering a new number in the address bar. Other than that, I don't know of a way to generate an index or discover what a particular e-novel really is.
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Slightly related, if you're a fan of 'vintage smut', there are several sites on the web worth a visit. Both sites have cover images of the items they're selling.
https://triplexbooks.com/ - Triple-X is one of the best - digital copies of vintage paperbacks
http://www.adultbookcovers.net/x-cart/s ... rch&page=1 - Adult Book Covers (ABC - get it?) also has a significant collection of vintage material - not just the covers
Both of the above charge a fee and deliver electronically. Triple-X used to have some original paper vintage books for sale as well.