Unfortunately, we do not keep a history of the eBooks you've read. We do this for privacy purposes. The library does have a way to "turn on" a history tracker (log in to My Account to do this), but that will only keep up with the stuff you check out via the physical library and not via the Library2Go/Libby/OverDrive or Cloud Library services.
If you have a Kindle, you should be able to see everything you've checked out and downloaded to your Kindle, as long as you never deleted the title from the Manage My Kindle webpage: http://amzn.to/OX3Mmu. Amazon automatically tracks everything you read on your Kindle.
