i would just add that the answer should be obvious, to the questions of where to PUT or where to GET digital books - the answer is: "any server on the internet is sufficient" - the web (aka: HTTP) was designed specifically for that very purpose, and for that purpose exclusively - HTTP uses, not surprisingly, the intuitive 'PUT', 'POST', and 'GET' requests as among the it's common "verbs"
the only reason i can imagine DRM being part of the question, is if some publishing "platforms" would require or inject DRM - they probably all require running non-free javascript to read about and access the work also - but no one needs any "platform" nor "publisher" for this - anyone with a computer can publish it, and anyone else with a computer can retrieve it - IMHO, the best source for a published work is directly from the author, if the author is concerned about fair or ethical distribution - any search engine would be sufficient to direct people to the resource, if one knows in advance that such a resource may exist so what this question is really asking, is for a third-party service which can help to advertise the existence of the resource to a wide audience - it is one of the most common arguments (though misguided) against self-hosting: "but how will people find me?" - answer: "that is why search engines were invented" for any digital work, the concept of a "publisher" is obsolete - this question is asking for a "distributor" or a "marketer" - that is a very different concern from "how to publish?" or "should i use DRM?" - it is a sad state of affairs, if people (especially libre-minded people) generally see those concerns as intrinsically entwined WDYT?
