Don't bet on it. Companies do not adopt cost-cutting technology to pass the savings on to the customer, they do it to increase profit margins. Consider cassette tapes (in the rare instances that they are available) versus CD's. CD's are far less expensive to produce yet they sell for a higher price. The same is true of VHS vs. DVD's. Using the same system to price PDF file book, you'd have to pay 3 or 4 times the cost of a physical book for that kind of "convenience and portability." If they could figure out an effective security mechanism you'd see lots more books in digital format. Some digital only.

As far as the book goes, I got a copy from my library through InterLibrary Loan just last week. I'm glad I did, it's definitely worth buying and I will when I have to give this one back. They won't have a digital version, but you might check out www.abebooks.com. It's a cooperative of independant book sellers with an online inventory system.