I have discovered something that may be useful for the rest of you.
Create multiple editions of your book. Don't settle for a nice trade paperback with 12pt font.
Make multiple large print books in various trim sizes. Be sure you create an ebook. Look at
http://www.smashwords.com. You can upload your book there for free (be sure to follow the formatting rules) and okay distribution to multiple sites. Smashwords is spreading their ebook formats all over creation (and further). Not only will your book be available through Smashwords, but will also be uploaded to Barnes & Noble, Kindle, Sony, Smallbooks, and others coming soon.
I have four editions of my book "Tales of a Texas Boy." All of them are available through Amazon and B&N. I've got the standard 12pt Garamond, an 8.5x11" Large Print, a 7x9 Large Print, and I am now producing a 6X9" Large print edition.
Take advantage of CreateSpaces's new distribution options. The more places your book appears, the more likely you'll get a buyer.