I emailed the Philadelphia Library about no new additions and here's the response I got:
Hello,
Thank you for your email. You are correct. We have added fewer titles than usual to our Overdrive collection in the past few weeks. Our priorities for licensing ebooks are to fill holds for people who are already on the waiting list for particular ebooks and then to add new best sellers to our collections. However, as the our fiscal year comes to a close we have had to adjust our purchasing for the library's limited budget. We hope to begin adding new titles soon as our budget allows. In the slightly longer term, our purchasing will return to normal when our new budget year begins on 7/1/2015.
Also, in the meantime, please also take a look at our Freeding collection of ebooks. Here you'll find titles that are not available in Overdrive. Also, if you are a fan of audio books, take a look at Hoopla and OneClick Digital. You'll find links to our Freading, Hoopla, and OneClick sites on our Digital Media page:
http://search.freelibrary.org/digitalmedia.cfm
I hope this information is helpful to you. Thank you,
Jamie
Free Library of Philadelphia