For those of us of a certain age, it’s hard to escape the trend in digital books. Nowadays Amazon, Sony, Apple and just about everyone else has an e-book reader. The numbers don’t lie. According to a May 19 announcement from Amazon, that company now sells 105 e-books for every 100 paper books.

I regularly see articles written saying that no seriously literate person would give up "real" books. Well, maybe someday, but you’re not prying those leather-bound collections of dead tree scraps from their hands any time soon.

So what is really happening? Who exactly is buying e-books, and what are they using to read them? Amazon also shows that it has sold three times as many e-books through May as the same period last year, so this mania is accelerating.

The sales figures indicate that e-book sales are rapidly increasing across all book categories from adult fiction to children’s books. Part of this is due to the remarkable popularity of Apple’s iPad, which makes a better e-book reader than most of the dedicated e-book readers. In addition, there’s an even larger universe of Apple iPods and Android smartphones, all with screens that are not much smaller than an old paperback page.

With free downloadable e-book readers for all of these devices from every bookseller, it’s hard to find anyone in high school or college who doesn’t have some books on the smart device in their pocket.

While the e-book sales numbers are now huge, they represent only a portion of the e-books out there as numbers are collected only on the e-books that are sold. If you haven’t used an e-book reader, you might not realize the tremendous wealth of free books. (These include almost every book you had to read in school.) None of these are counted in Amazon’s sales data.

If you want to try an e-book reader on your iPod Touch or iPhone, I would recommend Apple’s iBook reader, which has one of the best selections of free books available. If you don’t have Apple devices, try the Stanza (www.lexcycle.com) reader, which provides access to a wide range of public sources for free books as well as new books. And there is always Google’s free reader for Droid devices.

I haven’t bought a paper book in two years.