Although there are many sources of ebooks without use restrictions, it seems like most of them actually originate with a small handful of digitization projects. One of these is Project Gutenberg in concert with Distributed Proofreaders.

Is there any good source of information to show to what degree the top digitization projects are the source of the mass of unrestricted ebooks?

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    This looks like a duplicate of ebooks.stackexchange.com/questions/188/… Dec 23, 2013 at 18:43
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    There is a difference. I am asking about digitization efforts like Google Books Library Project, not packaging and distribution efforts like manybooks.net. Furthermore I am asking about the few efforts that digitize books by the tens or hundreds of thousands, and how those few stand in proportion to the sum total of digitization efforts.
    – minopret
    Dec 23, 2013 at 19:04
  • That is a reasonable argument; I have retracted my close vote. Also I can see where the answer would add value. Not sure where you find the answer though. Dec 23, 2013 at 19:09
  • The best central location I am aware of is archive.org it looks like it does capture a pretty wide base from Wikisource to Project Gutenberg are you looking for something more then this? Dec 23, 2013 at 19:12
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    You seem to be equating "digitization" with "unrestricted" availability. There are many modern books that are freely available because their authors chose to make them available. Here's a catalog: theassayer.org
    – user276
    Dec 28, 2013 at 20:19

1 Answer 1



I am assuming that the poster of the question calls "unrestricted books" the books that have no DRM, i.e., no technical devices intended tp prevent some uses, such as copy, search, or adaptation to new reading devices. All books are born legally restricted by copyright, at least today, until they enter the public domain. Very few rightsholders fully remove copyright restrictions by providing adequate public licences.

Though I have read many papers on the topic, and written some, I doubt there is such a document as requested in the question. The reason lies in the diversity of objectives of the numerisation projects, on the lack of standard definition of what a book is, on the wide variations encountered on book counts in various studies (notably those concerned with assessing the proportion of orphan books in various libraries). The definition of a book depends on a variety of parameters, including content and purpose, commercialization, relevance of distinct editions, choice of illustrator, each of which may impact some numbers by an order of magnitude. Does the Bible count for one, or for one hundred thousands? What about Shakespeare's works, or Alice in Wonderland? Does a single poem count as a book? What about a short story, a music score, a ship log, a catalog, a birth registry? Recall that what figures may be available may have been computed with different issues or purposes in mind, hence with different visions (often not explicited) of what counts as a book, and of what counts as two different books. Hence, rather than pointing on a specific document as requested, I try below to give a direct answer, based on figures I may remember or retrieve. But a short crisp answer would be misleading given the very fuzziness of available information, and the fact that the question itself is thus unwittingly very imprecise.

Global assessment

The production of unrestricted books by Project Gutenberg and similar projects is tiny compared to raw digitization and OCR, as donne by Google and large public and academic projects, for example by national libraries. It is on the order of 100 000 books, a magnitude order of 1/1000th of the total number of books, that seems to range somewhere between 50 and 130 millions, depending on how books are counted. Large digitization projects like those led by Google, National Libraries and large institutions are about two orders of magnitude more productive, some producing several millions of digitized books, though exact numbers are sometimes hard to assess.

However, if you consider quality digitization with proofread text and structured formatting like the epub standard, efforts like the Project Gutenberg seem significantly more productive, as large digitization projects produce only a few thousands, unrestricted, quality e-books (from what I have been able to check).

This is not surprising since large digitization projects are intended mostly for preservation purposes, and for accessibility by the research community (or for indexation purposes in the case of Google), while Project Gutenberg and its likes are intended for availability/accessibility purposes, i.e. to give convenient access to existing literature to a wider reading public. Raw digitization for conservation performed by large project is fairly cheap and fast, while quality digitization require long and costly human intervention (about one order of magnitude higher), that can be well covered by crowd-proofreading and editing.

Another aspect is that, while the total number of books is very large, only a small fraction is of interest to a wide audience. So the relevant corpus for Project Gutenberg is probably much smaller than the relevant corpus for large digitization project that have to deal with all kinds of archives, inventories and the like. This is compounded by the fact that the books that are of interest to a wide audience are to a large extent still under copyright, hence much less likely to be made available legally without restrictions, by any digitization project.

This actually stresses the importance in the book count of orphan books, and more generally of books not cared for by rightholders, and whether they can, or cannot, be made legally available, with or without restrictions. This may represent on the order of half the books in copyright. In the USA, it is an important aspect of the legal battle around the Google Book Search Settlement Agreement, and it is the object of a specific law in France.

So, I would tend to believe that cooperative projects like the Project Gutenberg are the major source of unrestricted ebooks, if you consider reading resources for a wide public. But, it makes little sense to compare the output of two types of projects that have different purposes, at least in the medium term.

Still, it should be noted that preservation is probably a more urgent task than high quality digitization. It is rather sound that preservation projects will avoid diverting much of their limited resources on costly high quality output, other than for public relation purposes. Also, the mass of documents digitized by large projects provide a good source of raw material for smaller projects (in size) that are aiming for quality output that has a chance of attracting some readership.

We should also remember that digitization is not the only source of ebooks. There are authors, publishers and institutions that produce a very significant number of new books without DRM restrictions, though there may be legal restrictions on use not enforced with DRM, as was the case before with classical paper books.

Though I spent significant time analyzing the question and writing the answer with some figures to substantiate it, it ended up being far too long, and messed up by the heterogeneity of sources. Hence I decided to cut it short here. If interested, you may read the rest in a previous version from the history of this anwer, which contains some additional figures and references from various projects.

2 related questions:

What kinds of DRM are used in eBooks? Is it possible to purchase DRM free eBooks?

Some classic literature is available for free - but where?

  • Thanks for your work at sharpening the question! Good, I could edit it or ask afresh to address specifically the quality availability of orphan books for a wide public. It sounds like, as I imagined, PG may be the major origin of those. The point of interest to me is that multiple other projects appear to repackage those books from PG - with PG's encouragement AND, if modifying them substantially, explicitly prohibited from claiming they originate with PG - leaving the origin of those texts a bit mysterious
    – minopret
    Jun 25, 2016 at 12:45

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