I just looked up my own O'Reilly book on ebooks.com.
http://www.ebooks.com/95729334/designing-data-intensive-appl...
I can't see anything about DRM on the page, but under "supported devices" it says "e-readers with Adobe Digital Editions installed". Isn't that DRM enforcement software? Could you clarify please?
I am not sure if your book is DRM protected – if you browse the books at ebooks.com, you will see that ebooks.com is selling books in "EPUB/PDF format" and „secure EPUB/secure PDF format“. Furthermore please take a look at https://support.ebooks.com/hc/en-gb/articles/205639205-Insta...: Most of the ebooks available to download from eBooks.com (but not all) are protected by Adobe DRM…