In 2017, books formerly on the Ebrary and Ebook Library (EBL) platforms were migrated to Ebook Central (EBC).
Viewing an Ebrary book on a Kindle Fire is possible although it requires some extra steps due to Amazon’s proprietary software.
Ebrary has offered some helpful advice here.
Additionally, you can email e-books to your Kindle account or you may be able to "print" to a .pdf and then transfer to the Kindle.
We own a number of e-books from Ebook Central, but for the majority of them we subscribe to access. The ability to access any of these titles will vary according to publisher restrictions. Some may be downloaded a chapter at a time and some may be "checked out" for some preset period--14 days is usual. You will need to create a personal account with Ebook Central (there is no charge for this). E-books with Single User access may not be downloaded/checked out, in order to preserve access for other users.
For the subscribed access (titles within Proquest Ebook Central Academic Complete) we have unlimited user access. However, these titles are also subject to removal semiannually. According to Proquest, "Title removals from subscriptions are mainly due to requests from publishers or to achieve parity across subscription products."
User access restrictions are noted on the landing page for each e-book.
For additional information about their e-books, Proquest has created a very thorough LibGuide: