Guidelines for assignment to e-books

About ISBNs and digital publications

ISBNs are not only for print books; in fact it is of no relevance in what medium a publication is made available. Provided it is text-based, available to the public and a one-off (not serial) publication then it will qualify for ISBN assignment. ISBNs should be used to identify each separate digital publication (including apps) and guidance on how to do this is given here.

What is a separate digital publication? 

In order to reach the widest possible market, a publisher or retailer may make a particular e-book title available as multiple product options. Although the editorial content will be the same, if a specific device or software is required to read the e-book or different usage constraints that control user functionality are offered (e.g. copy, print, lend etc.) then each separate version will be a distinct product. Each distinct product that is available must be identified by its own ISBN as it is a separate publication. Thus, a separate publication is normally defined by a combination of product form features or details and usage constraints.

What if the e-books are all in the same format (e.g. EPUB)?

If the different versions are in the same format and use the same DRM software (e.g. Adobe ACS4) with substantially the same usage constraints and are interoperable on different devices or software, then a single ISBN should be used. If, however, the same DRM software is used on two versions but with significantly different usage constraints (e.g. one allows printing but the other does not) then each version should have its own separate ISBN.

If proprietary DRM is used that ties a version to a specific platform, device or software then, if ISBNs are assigned, separate ISBNs should be used for each such version.

How are “master files” treated? 

Publishers often provide a single master file to a conversion service but may not always specify the different combinations of file format and DRM which the conversion service will provide to retailers. Unless it is also being made available to the public in exactly the same form as the master file (i.e. unchanged file format and without DRM applied) then you should not give an ISBN to the master file. However, you should assign separate ISBNs to each version that is subsequently generated by the conversion service. If your legacy computer system requires an ISBN to identify a master file, then this should be kept as a purely internal identifier to avoid the possibility of several different versions carrying the same ISBN.

What about proprietary formats (e.g. Amazon Kindle)? 

Some retailers are the sole providers of e-books in a proprietary format that can only be bought through their website. An example is Kindle format e-books which are only available from Amazon. In this particular case as there is one source of supply, the retailer does not require ISBNs and so it is not strictly necessary for the publisher to assign an ISBN to this particular version. Publishers can assign an ISBN if they wish, for example if it is useful for their own purposes or they want that version to be listed in third-party databases of available e-books .As these platforms are generally not interoperable, if ISBNs are assigned they must be unique to each version so as to avoid identification problems if those versions should later become available through third parties. 

What if publishers don’t assign separate ISBNs for each version? 

Publishers should provide their conversion service with all the ISBNs that they will need to identify each of the versions that they will produce. If a publisher will not provide ISBNs to intermediaries for this purpose then, as a last resort, intermediaries may assign their own ISBNs. ISBN agencies will provide ISBN prefixes to intermediaries for this purpose. In this case ISBNs and related metadata should be provided back to the publisher and to the national ISBN agency and other bibliographic agencies.

Note that the assignment of an ISBN has no implications for rights ownership.

What if e-book devices don’t support different features such as type size, text to speech, bookmarking, colour, etc? How does this affect the assignment of ISBNs? 

Although the content, file format and DRM usage constraints will be set by the publisher or intermediary for a particular e-book and delivered to the user in this way, it is still possible that the user experience may vary according to the device or software of the user. When the variation results from limitations of the capability of the device or software used to read the e-book then this does not impact on ISBN assignment. The same ISBN should be used because the same product is being delivered each time.

Note that provision of mono or colour images in separate e-publications intended respectively for mono or colour devices constitutes a change of content – and therefore of ISBN. However if colour images are provided, but a particular device has only a mono display, that is simply a device limitation and does not imply a second ISBN.

What about enhanced e-books? 

When an e-book is available in enhanced form and includes audio, video or other additional content, it will qualify for ISBN. If the e-book is also available separately without these extra elements then these are different products and should therefore have separate ISBNs.

Can e-book “apps” (e.g. applications for iPhone, Android etc.) have ISBNs? 

Yes, provided that there is significant textual content. An e-book app is simply a combination of textual and other content and software. If the software element changes (e.g. it is targeted on different operating systems), then each version should have a separate ISBN. If the app is only made available through a single source, then ISBNs may not be necessary.

What about different types of DRM? 

It is possible that an e-book may be available at the same time either with no DRM at all, with different DRM software or with “social” DRM applied. If the “social” DRM version does not intrude significantly on the user’s experience, does not enforce any usage constraints and is transparent to the user then it need not be given a separate ISBN from the version with no DRM at all. However, if the different types of DRM are used to enforce different usage constraints or enable/disable certain features, then separate ISBNs must be assigned.

Is there a standard way of describing different product forms and DRM features? 

ONIX for Books is the international standard for representing and communicating book industry product information in electronic form. The latest release, 3.0, has improved handling of digital publications and provides structures for describing product form detail and DRM usage constraints. Even if you do not use ONIX, you can use the standard codes to describe product form and usage constraints that are included in the relevant sections of the code lists (DRM–related codes, lists 144-147; product content type, list 81; product form detail, list 175).

Further information on ONIX for Books 3.0 and code lists is available from EDItEUR

How can all the different versions of an e-book be linked together? 

The ISTC (International Standard Text Code) is a new ISO identifier that identifies the underlying textual content of the book and is therefore shared by all digital and physical manifestations of the same title. The assignment of ISTCs can facilitate the linking of all versions and, with the addition of a filtering element such as product form, could also be used to link all e-book versions. Some systems already use an internal work identifier to provide this functionality but this cannot be used in the supply chain.

Note that the implementation of ISTC can support metadata being inherited from work level to manifestation level and can save rekeying.

Further information on ISTC is available from the International ISTC Agency.