Print vs. electronic books: Which format sells best online? The short answer is print. By 80%. But, while you are fussing about format, most buyers aren't.

Delivery method is secondary. The value and benefit to readers is
the information. If they want info, they’re going to go online and try to find it, then ask, 'great, how is it sold? Can I get it delivered?' Publishers make a mistake when they think they are selling books. They are not. They are selling information or entertainment. When they begin to look at what they own that way, they can see other ways to slice, dice, and deliver.