I've become more and more aware of the limitations of my library's ebook collection (via Overdrive). It seems like the number of bestsellers--and the total number of books of any variety--shrinks every year. My library recently dropped its non-Overdrive e-service, and, rather annoyed, I decided to see what was going on.
There's been reports for years that Overdrive cynically manipulates the available collections to various libraries, making both standard charges and base collections effectively opaque to libraries.
What I didn't realise, however, was just how expensive Overdrive books actually are.
According to one of the articles I found (emphases mine): 
Simon and Schuster will not license ebooks to libraries.
MacMillan does not make ebooks available to libraries.
Hachette, in general, does not make frontlist titles (titles newer than 1 year) available to libraries, and they have increased their prices roughly 220% in the last year.
Random House currently licenses both frontlist and backlist titles (older than 1 year) to libraries, but they have raised their prices roughly 300% in the past year, with some titles reaching $100.
HarperCollins will license ebooks to libraries, however each title can only be circulated 26 times. After 26 readers have checked out the title, the library must repurchase it.
Penguin ended its relationship with Overdrive, MVPL’s ebook provider in early 2012. Penguin has blocked support for Kindle titles, which is why some Overdrive Kindle ebooks can not be transferred wirelessly, but must be side loaded.
Another source has an apparently more recent list; the major change seems to be that Penguin is again offering ebooks to libraries. HarperCollins' 26 circulation restriction is still in effect. Macmillan expires books after 2 years or 52 checkouts. Random House has no restrictions, but charges approximately 3x-4x more than consumer prices. 
Douglas County Libraries (Denver, CO) publishes monthly charts that compare library/consumer pricing between print/ebooks for the top-20 Amazon books.
This month, The Goldfinch, which costs consumers $15, costs $90 on Overdrive. The library binding is still about $16.
However, I think the biggest shocker for me was the Project Gutenberg books.
Did you know that Overdrive charges libraries for public-domain books? According to , Les Miserables, which is a free ebook from Amazon and Gutenberg and is about $11 in paperback costs $78 on Overdrive. (Why on earth, then, is my library still wasting money on classic ebooks?)
On the positive side, I don't blame my library for its sorry circulation any more.