By Matt Brownell, MainStreet

E-book sales are set to get bigger and titles to get cheaper over the next two years, according to a new report from the Yankee Group, a Boston research and consulting firm.

Released this week, the report projects big gains for the e-book market: Consumers will purchase 381 million e-books by 2013 -- quadruple the total purchases made in 2010 -- and bring total revenue to $2.7 billion that year, according to the report. Calling it "the next big gold rush," researchers project e-book sales will grow at an even faster rate than that of mobile apps over the same period.

The projected sales explosion likely comes as no surprise to retailers like Amazon (AMZN) and Barnes & Noble (BKS), whose respective Kindle and Nook e-readers lead the field. Both companies have said their e-readers are their best-selling products of all time, and Barnes & Noble announced in December that its e-book sales now exceed those of print books.

So who will be the big winners in the e-book boom, besides Amazon and Barnes & Noble?

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Interestingly, it's consumers. Average e-book prices fell 50 cents in 2010, and that trend is expected to continue over the next few years, as the report projects that the average e-book will cost just $7 by 2013. Consumers unwilling to pay that much may also begin to see alternative business models, including ad-supported e-books and rentals.

There do seem to be plenty of readers who haven't gotten on board with the e-book craze. While a solid 20% plan to stop reading print books or already have, half the populace says it will never part with "real" books in favor of the electronic kind.

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