In the weeks leading up to the release of Apple's iPad, many publishers rushed to complete agreements that would switch their e-book pricing terms to the agency model to make sure their titles are available to read in the iBooks format, a proprietary Apple e-book format optimized for the iPad's size and functionality. But while most large book publishers—excepting Random House—and some smaller publishers are now available as iBook editions, those that are not can still claim their books are available to read on the iPad because the device continues to support iPhone e-book reading apps.

Consumers who use Kindle on iPhone, Kobo, or the other popular iPhone reading apps can continue using those apps and others on the iPad. Indeed, it could be said that publishers that have not switched to the agency model may have landed in the best of all possible e-book worlds—their books are available on the iPhone as well as the iPad, the hippest consumer device released in years; e-book pricing (including Amazon's $9.99 de facto standard) essentially remains the same; and publishers can monitor the volatile infant e-book marketplace to see how consumers are responding to new pricing polices and a proliferation of new reading devices.

E-book apps that are currently optimized for the iPad include Kindle on iPad, Kobo, and Comixology for iPad and the newly launched Marvel Comics iPad app, both of which were designed by Comixology specifically for reading digital comics. Among the better known e-reading apps that are not yet optimized for the iPad's arrival are the B&N/Fictionwise eReader, Stanza (which is owned by Amazon), ScrollMotion's Iceberg Reader, Adobe Digital Editions, and Blio, Ray Kurzweil's much demoed, hyped, and anticipated e-reading software, due to be unveiled this spring in collaboration with Baker & Taylor.

Developers of e-book software are scrambling to develop new versions of their iPhone e-book readers optimized for the larger format iPad—even though, by all accounts, iPhone e-book apps work just fine on the iPad. iPhone apps will run on the iPad at iPhone-size or can be scaled up to the larger iPad size without much loss of clarity. Nevertheless, developers are frantic for their e-book apps to be seen as iPad optimized and are often reluctant to even admit that they have not released an iPad version.

While a spokesperson for Stanza told PW, “At this time there is no work being done on an iPad-optimized version of Stanza,” other developers seem keen on having an optimized-for-iPad e-book app. B&N's spokesperson Carolyn Brown was quick to emphasize, “We will have an iPad app in a few weeks.”

If you're Random House, Harlequin, McGraw-Hill, or O'Reilly Media—publishers that have not gone to the agency model—all the books you have traditionally offered on the iPhone through B&N/Fictionwise (about 300,000 e-titles), Stanza (about 600,000 titles for sale from a variety of e-retailers), and ScrollMotion's Iceberg Reader (probably thousands) continue to be available on the iPad. In fact, the iBookstore only offers about 60,000 titles for sale, although Apple has announced an iPad/iPhone version of the iBook reader to come this year that will allow users to synch their iPhone and iPad titles.

The Comixology iPhone/iPad app offers about 1,300 titles and the newly launched Marvel iPad app offers 500 Marvel comics. Set to launch with free downloads in the spring, Blio is said to offer about 220,000 titles from 70 publishers that can be read on PCs, Macs, and the iPhone. However, spokespersons for Kurzweil's company, KNFB Reading Technology, and for Baker & Taylor declined to say whether an iPad version of the Blio software would be available when Blio is launched.

In the age of digital reading, the reading app has become just as important as the device that supports it. And any sense that a reading technology is not cutting-edge current may diminish it in the eyes of consumers.