I am a lifelong mystery fan (especially the Golden Age stuff) - and since acquiring my Kindle have been emailing publishers that I currently buy pbooks from to see if they have any plans to offer electronic versions.
Here is the reply I received from Rue Morgue Press today:
"No plans to do so. There isn't much out there other than Amazon's Kindle (and Sony Reader) and we have rejected offers from Amazon, as of course Kindle is a proprietary property and so by letting them do it means that we give them an advantage over all the other bookstores. In fact, we're boycotting the World Mystery Convention because they're allowing Amazon to make a Kindle presentation."
Several aspects of this reply strike me as sad. One, they are aware of the existence of only 2 readers. Second, the continuing battle between Amazon's proprietary business model and smaller publishers. Three, the effect of publisher boycotts on the future availability of classic mystery titles still under copyright for readers that are moving to eBooks. Of particular interest to me are: Ngaio Marsh, Elizabeth Daly, Dorothy Sayers (two Wimsey titles are now PD), and Gladys Mitchell.
I will forward answers as I get them from other publishers.