Hi, I'm Nathan.Sorry to hear that you're having trouble, but I'll do my best to help you. Please give me a few moments to review your details here.
Are these kindle books that you are referring to (on the nexus) that were purchased from amazon?
OKay if that is the case, no transferring is really necessary.All your previous book purchases are still linked to your amazon account, and stored in the cloud and always available to you.
All you have to do is register the knew kindle to your existing amazon account, and all your book purchases will show there, just look under the CLOUD library rather than Device library, and as you select each one, it will download to the new kindle for local storage and offline use on the new kindle.
If you have any other questions, just let me know. Otherwise, please take a moment to rate my service as this is the only way I am credited for my time. Hopefully I have earned 5 Stars but if not please let me know what I can do to ensure you are satisfied. I also invite you to contact me directly with any future support needs at http://bit.ly/1QwLxGh and ask for Nathan.
Thank you, ***** ***** a nice day,