Bnc Tech Forum 2010: Designing ebooks for ePub reading engines

Open source ePub:
Digital Books

Liza Daly
Threepress Consulting Inc.

Thursday, April 1, 2010


This is the collection of ereaders and mobile devices I have at the office. I use them to test
ebooks as well as report on the capabilities of the various hardware readers out there.

TextPlus one netbook, two Macs, one Windows laptop,
and an iPad (on order).


That doesn’t even count the most popular ereading devices today: the multiple computers,
netbooks and tablets.

?

The challenge: How do book designers and publishers effectively design ebooks for large
screens, small screens, and screen dimensions and platforms that haven’t launched yet?

Thinking about devices


Thinking about devices

Thinking about reading engines


I’d like to propose that we change the conversation from thinking about speciﬁc devices
(which multiply every day) to thinking about “reading engines.”

Reading engines
put text on the screen


A reading engine is the part of the ereading software that actually places text on the screen.
It’s the most basic, primitive component of any ereader.

WebKit
Adobe
Reader
Mobile
SDK
Mobi: fail


Fortunately for ebook producers, there are far fewer reading engines than devices. This talk
will focus on the two most popular reading engines for ePub books: Adobe Reader Mobile
SDK (RMSDK) and WebKit.

Adobe Reader Mobile SDK

Software that is licensed to
device-makers and software
partners to provide Adobe’s
EPUB support and DRM.




RMSDK doesn’t technically power Adobe Digital Editions, but it’s very close in terms of its
behavior.



RMSDK includes both the reading engine and the DRM server. Licensees get both, so in most
cases if a reader supports Adobe EPUB DRM, it uses the RMSDK reading engine.

With great power...
• Almost industry- • Limited CSS support
standard DRM
• No support for foreign
• Consistent rendering characters (without font
across devices embedding)
• SVG support • Narrow default margins
• Flash support • Multimedia only via Flash
• More precise pagination • Adobe-only extensions
and layout controls


There are some advantages and disadvantages to this approach. I’m going to focus on how to
turn the disadvantages into cost savings during ebook production.

...at least the bugs are
consistent


Once you understand what uses RMSDK, it’s possible to see the same issues across many
different software programs and devices.

Readers using the RMSDK:

• Digital Editions • txtr
• Sony Reader • Spring
• Sony desktop reader • PlasticLogic
• Barnes & Noble nook • Kobo Reader (device
• IREX only)


WebKit


WebKit powers a number of different web browsers and mobile browsers. If you’ve used
Google Chrome, Safari, the iPhone/iPad/iPod Touch, Android or Palm Pre/Pixi, you’ve used
WebKit.

WebKit


Though there are other browser engines on the desktop web (IE, Firefox’s Gecko, Opera),
WebKit has quickly dominated the mobile web.

WebKit


and it’s expected to grow as other kinds of mobile devices replace their own browsers with it.

Ereaders using WebKit


Although WebKit isn’t technically a reading engine, because ePub is so similar to web
technologies, it makes an excellent tool for building an ereader. Most mobile ereaders use
WebKit, and any browser-based solution (Bookworm, Ibis Reader) will be using it on the right
browser. iBooks is almost certainly WebKit-based.

Ereaders using WebKit


Some devices are hybrids. The Spring Design Alex ereader uses both RMSDK and WebKit, via
its built-in Android browser.

WebKit vs. Mobile SDK
(Barnes & Noble vs. itself)


Some ecosystems are also hybrids. Kobo also follows this pattern, where they have a custom
WebKit-based software for computers and mobile devices, but RMSDK on hardware devices.

Designing for 99 devices


Designing for 99 devices
Designing for 2
reading engines


So thinking about reading engines can really simplify issues around ebook design.

Surviving Digital Editions

Avoid Adobe-speciﬁc
extensions...
...except to solve Adobe-
speciﬁc problems


Here are some techniques for optimizing for the Adobe ecosystem without affecting the
validity of your ebooks.

Mostly harmless

Page templates (XPGT)
control the layout and
ﬂow of pages in ADE-
related reading engines
http://blogs.adobe.com/digitaleditions/template.html


Mostly harmless

XPGT lets you control
page breaks and widths
of columns in RMSDK
software, and still
produce valid ePubs
http://blogs.adobe.com/digitaleditions/template.html


Mostly harmless

Work around RMSDK’s
poor international font
support with embedded
open-source fonts.
http://blog.threepress.org/2009/09/16/how-to-embed-fonts-in-epub-ﬁles/


Considered harmful

InDesign font obfuscation
isn’t compatible with
other systems and isn’t in
the ePub spec.

http://blog.threepress.org/2009/09/16/how-to-embed-fonts-in-epub-ﬁles/


Considered harmful
ADE will only display the
ﬁrst dc:author - don’t
work around by adding
multiple authors in a
single ﬁeld.
That’s bad metadata!
http://blog.threepress.org/2009/11/27/practical-epub-metadata-authorship/


Considered harmful
Adobe’s page-map,
mapping print pages to
ebook “pages,” is not in
the ePub spec and won’t
work anywhere else.
http://blog.threepress.org/2009/11/26/adobe-page-map-versus-ncx-pagelist/


Designing for the future of ePub
Keep markup minimal and semantic.


Keep markup minimal and semantic.

Specifying the spacing between a header
and body text is presentational.

Specifying some spacing between a scene
change is semantic.


Some tips that will work well in WebKit and all future ePub implementations include being
thoughtful about what design elements are speciﬁed in the book. Try to keep to purely
semantic markup and styling.

Restrict CSS to inside the content.

Prefer padding to margin.

Use Adobe’s extensions to handle page
breaks and margins; let other readers
decide for “themselves.”


Test and preview in:

RMSDK
Big WebKit
Little WebKit


My recommended testing paradigm: test in one RMSDK device/software (usually ADE), one
“big WebKit” like a web browser or iPad, and one “small WebKit”, or mobile device or browser.

Multimedia?

No HTML5 in ePub...
...but no Flash on the iPad


Designing for the future of ePub: what about multimedia? Unfortunately Flash is no longer the
easy answer. HTML5 <video> adoption will come to ePub eventually, but for now it will
produce invalid ebooks in most case.

These companies are betting HTML5:

and provide signiﬁcant resources for WebKit
development...


However, looking ahead, I think the smart money is on what Google and Apple are doing.


...means designing for WebKit


This doesn’t mean that you should ignore the Adobe ecosystem! It’s the most signiﬁcant part
of the marketplace right now. And don’t design two different ebooks -- all these techniques
can be used in the same ePub ﬁle successfully. But in my opinion, the future will be browser-
like reading engines.

Thanks!
Liza Daly
Twitter: @liza
liza@threepress.org

http://threepress.org


Bnc Tech Forum 2010: Designing ebooks for ePub reading engines

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