I've put four of my recent SciFi novels online for free, and if it proves popular, I'll rotate through more from my backlist, for which I have to remove them from Kindle Unlimited as part of Amazon's terms. If you don't want to fool around with downloading files and side loading, I've formatted them for reading on a phone or any other device, and the browser should remember you place, even if you close it.
I'm trying to rationalize my websites going back decades so I've concentrated my free SciFi, as ePub and AZW3 (Kindle) downloads or to read in the browser on my other website with the list of over 350 free classic science fiction novels and stories took quite a bit of research to put together. It includes books from modern SciFi writers which first appeared in pulp magazines, classic out-of-copyright, and earlier works of speculative fiction that not everybody will agree are science fiction.