Ten US universities are offering digital versions of assigned books this fall. “Alongside the new and used versions of Dante’s “Inferno” and “Essentials of Psychology” will be little cards offering 33 percent off if students decide to download a digital version of a text instead of buying a hard copy. That’s not a bad deal for a cash-strapped student facing book bills in the hundreds of dollars. But there are trade-offs. The new digital textbook program imposes strict guidelines on how the books can be used, including locking the downloaded books to a single computer and setting a five-month expiration date, after which the book can’t be read.”