As you may or may not know, Amazon has released a new ebook reading device -- Kindle.
Harlequin is very committed to providing ebooks in ALL formats, so it has released its front list and back list in Kindle. I believe ebooks are released to other sources besides eharlequin on publication date. So this means that The Roman's Virgin Mistress is available in the Kindle format now and A Christmas Wedding Wager will be available in Kindle on 1 December.
I have no idea about ebook readers as I do not own one, but some people swear by them. I know they are very good for people who have failing eyesight and want large print at a decent price.