I publish both in print and ebook form. It's such a relief to be able to sell ebooks as it's so hard and expensive to promote print books.
With the print books we get most sales at live events with authors reading just about every month at different venues to keep the sales going. There's no income from it, really, because the cost of producing print books is just about equal to the income from selling them.
Authors get royalties from us, but it's so expensive for them travelling round to events too. So ebooks are a real bonus.
I would add to this that I also find that print books tend to sell when we have ebook promotions, so ebooks really help sell more print books. People worry ebooks will cut into print book sales, but this isn't true. Sooner or later I think most people will be reading ebooks, but at the moment they're the best promotional aid to selling print books, apart from live readings where people might buy a signed copy.
One reason it's so hard making an income from print books is that we have to set up the right distribution channel or bookshops and some online retailers won't stock them. We have to put the books with a distributor, which is really a glorified name for a warehouse, and bookshops will only buy if we do that. We then also have to go with the wholesalers the bookshops use to order books, and the wholesaler gets the book from our distributor. They each take a cut, so you get the picture about why it's hard to do more than break even. Amazon will only stock our books if we're with their wholesaler (and we are).
If you're using Print On Demand on Amazon your print books will be stocked by them. Print on Demand makes it harder to stock a warehouse/distributor and wholesaler, so it's much harder to get into other bookshops.
Giveaways and promotions on Goodreads etc may help, but I haven't tried them so I'm not sure.