After downloading the book to my computer, I was not sure how to transfer it to my iPad. A bit of online research revealed "BlueFire Reader" which authenticates with an Adobe ID. eBooks can then be "side-loaded" onto the iPad BlueFire Reader using iTunes.
From the website http://www.bluefirereader.com:
Bluefire Reader is built on the Adobe® digital publishing platform, the most widely used eBook distribution system. Our Adobe Reader Mobile based application supports ePUB and PDF content, including files protected by Adobe® Content Server encryption technology. Adobe® Reader Mobile is the industry standard for eReader devices and applications that support ePUB and PDF content.
Bluefire Reader integrates rich catalog presentation features, including in-app and web-based purchasing. You can also take advantage of Bluefire's advanced Open Publication Distribution System (OPDS) Services to make the creation and management of your book catalogs easier than ever before.