Historically speaking, people have gone to the trouble of manually digitizing hard copy books to distribute freely. There were digital copies of print books available online (if you knew where to look) before e-books were officially available for sale in any form. That includes mass-market novels as well as items of interest to historians. Ergo, your scepticism seems entirely unjustified.

OCR is far from perfect (though editing OCR output is generally faster than retyping), but even without it we have the storage and bandwidth these days to distribute full books as stacks of images if needed, without converting them to text. The same way people distribute scans of comics/manga.