Sales of electronic books are expected to hit nearly one billion dollars in the United States this year and to triple by 2015, according to a new report by Forrester Research Inc.

The market research firm said US spending on e-books was expected to total 966 million dollars this year, up from 301 million dollars last year and to reach 2.81 billion dollars in 2015.

Forrester said the number of e-book readers with dedicated devices in the United States was expected to grow from 3.7 million at the end of last year to 10.3 million at the end of this year to 29.4 million in 2015.

Seven percent of online US adults who read books read e-books, a number that is expected to double a year from now, Forrester said.

A Forrester survey of e-book readers found that 35 percent read e-books on a laptop computer, 32 percent on Amazon's Kindle, 15 percent on Apple's iPhone, 12 percent on a Sony e-reader and 10 percent on a netbook computer.

Nine percent said they use a Nook e-reader from Barnes and Noble, nine percent said they use Apple's iPad, eight percent said they use some other e-reader and six percent said they use a cellphone other than the iPhone.

Forrester also said Amazon's Kindle store "stands to benefit tremendously" from the rise in e-book reading because of its existing relationship with book buyers through Amazon.com.

Fifty percent of people who bought an e-book in the past month have purchased e-books from the Kindle store, Forrester said.