They don’t yet rival their traditional counterparts, but e-books are continuing to grow in popularity in the Anoka County library system, where they were introduced in January 2011.

From 2011 to 2012, the number checked out more than doubled, from about 48,000 to 112,000, said Jill Smith, adult services manager for the system. That was an increase from less than 2 percent of total circulation to about 4 percent.

Growth is continuing so far this year, with e-checkouts running more than 20 percent ahead of a year ago.

The number of titles in the library’s collection also is on the rise. It stood at 7,260 at the end of 2012, compared with 4,631 the year before.

The most popular e-books with readers? Romance and mystery novels, Smith said.

For e-reader and tablet owners who could use a hand, the system offers drop-in help from 5:30 to 7:30 p.m. Mondays at Northtown Library in Blaine and 6 to 7:30 p.m. Wednesdays at the Rum River Library in Anoka.