Seems like all the publishers and all the societies are trying to get into the eBook game. The newest announcement is from AAS (using IOP as a publisher). Considering the fact that a lot of these domains are not particularly known for monographs - like Computer Science and ACM's new ebook line - but instead for conference proceedings and journal articles, seems kinda weird.
Someone mentioned that maybe it was due to the ebook aggregator demand driven acquisition plans - but I think it's just the opposite. Many major publishers have jacked up prices (pdf) on EBL and Ebrary recently - all to push libraries in to licensing "big deal" bundles of the entire front list or entire subject categories. And it is super attractive to buy from the publishers because they're often without DRM, PDFs (one big publisher even offers a whole book in a single pdf, most are one pdf per chapter), ways to view online, easily findable using Google and also nice MARC records for adding to the catalog.
The ebook aggregators have nasty DRM. They have concurrent user rules. They have special rules for things that are considered textbooks. We have to login with our enterprise login (which isn't my lab's day-to-day login) and the data about what books we view is tied to our identities. The new prices end up being as much as 30-40% of the cover price for a 1 day loan. That's right. The customer can look and maybe print a couple of pages for 24 hours and the library is charged a third the cover price of the book.
But for the society and publisher own pages, what seems like a one time purchase has now become yet another subscription. If you buy the 2014 front list will you not feel the pressure to buy the 2015 and 2016 publications?
Aggregators had seemed like some of the answer, but not so much with these prices. We've already mugged all the other budgets for our journal habit so where do these new things come from? The print budget was gone ages ago. Reference budget was also raided. The ones we've licensed do get used a lot at MPOW.