[AnemicOak]

And format doesn't just mean ePub or Kindle, etc. If DRM is applied to an ePub then each version with the various DRM is a different format. In other words a "standard" Adobe DRM'd ePub is a different format from an Apple DRM'd ePub or a DRM-free ePub. However if the retailer, such as Amazon or Apple, is the only place to get a specific format of a book and if that retailer doesn't require ISBN's then an ISBN isn't required.



From the ISBN Manual (section 6.3)...
https://www.isbn-international.org/s...12%20-corr.pdf

End users need to know a) whether the e-book that they are purchasing will work on their device or software and b) what they will be able to do with it (e.g. copy, print, lend, text to speech etc.). This is normally defined by a combination of file format and software known as Digital Rights Management (DRM) which controls, by technical means, the use that can be made of the e-book. Separate ISBNs will facilitate management, dissemination and discovery of that information as well as delivery of the appropriate version of an e-book.

 Where a specific qualifying e-book is available in different file formats, each different format that is published and made separately available should be given a separate ISBN.

N.B. A file format is a particular way that information is encoded for storage in a digital file. In the case of e-books, the file format is often a combination of an underlying file type (such as EPUB, .pdf etc) and digital rights management software (such as Adobe’s ACS4, Apple's Fairplay etc.).

 Where proprietary DRM is used that ties a version to a specific platform, device or software, separate ISBNs should be used for each such version.

 Where digital publications are being supplied by a retailer that is the sole provider of e-books in a proprietary format that can only be bought through their own websites (e.g. Amazon Kindle, Apple i-books) and that retailer does not require ISBNs, it is not necessary to assign ISBNs to those versions, although it may be useful to do so for tracking sales or for listing publications in third-party databases of available e-books. If ISBNs are assigned, they should be unique to that version.

 A new ISBN may be assigned when a book is digitised by a library or other organisation under certain circumstances. If the electronic version is made available to the public, then as a new product it should be identified by a separate ISBN, regardless of whether or not there is a charge for access to the digital version.

 Where a publication is available in a supply chain with more than one specific type of DRM, whether offered by the original publisher or by a vendor later in the chain, then each of these are unique products that need to be identified by unique ISBNs.

Example 1: A publisher produces two EPUB versions of the same book, each with different DRMs and then distributes them through the supply chain, through different intermediaries. An ISBN is required for each of the specific
DRM versions of the product.

Example 2: A publisher produces a file in EPUB format and releases this to a
vendor who applies two different types of DRM to the EPUB and makes the two versions available separately, as two distinct products. An ISBN is required for each of the specific DRM versions of the product (the ISBN may be assigned by the publisher or by the vendor if the publisher does not do so).

Example 3: A vendor offers to the public the possibility to buy an e-book and to customise on demand the type of DRM to be applied. In this case, the DRM is applied at transaction level and there is no need to assign different ISBNs, since there is no ambiguity in the dialogue between the vendor and the buyer.

 If a publication is made available with different usage rights (e.g. adjusting the usage settings so that printing is allowed in one, but not in another), each version must be assigned a unique ISBN. In almost all cases usage rights are controlled using settings within the DRM software.

Example 4: A publisher releases a publication — one version of the publication is available with accessibility features such as text to speech (controlled through the DRM software) and one without. Each of the versions must have unique ISBNs in order that the particular attributes are clear to potential buyers and users (especially those looking for accessible publications) and so that the versions are separately identified. However, also in this case, when the usage rights are defined during the transaction between the vendor and the user, there is no need to assign separate ISBNs.

Example 5: A publisher releases a publication in one format with one ISBN and then offers to customers a service to acquire different usage rights on demand. Similarly to example 3 above, separate ISBNs are not required to identify the individual customised transactions.

 If publishers are using intermediaries to generate different formats of their e-books, then they should provide separate ISBNs for the intermediaries to assign to each format.

(N.B. The method outlined in this paragraph is not the recommended solution and should only be used in cases where a publisher refuses to assign individual ISBNs to each product).If a publisher will not provide ISBNs to intermediaries for each separate format then intermediaries may assign their own ISBNs. ISBN agencies will provide ISBN registrant elements to intermediaries for this purpose. In this case ISBNs and related metadata should be reported back to the publisher and to the national ISBN agency and other bibliographic agencies.