Ateneo Press uses Adobe’s Digital Rights Management (DRM); in order to access the e-book, you need to register your device/s with Adobe to open the file. While it is possible to authorize a device without an Adobe ID, it might make it harder for you to open your e-book across several devices. Signing up for an ID will allow you to download the book on six (6) devices. Click here to sign up for an Adobe ID.
For more instructions on how to get your e-books, proceed to "Do I need a special device or program to read by e-book?"