I haven't been able to find such an app. There are several apps here that dynamically pull from amazon reviews but not goodreads reviews, even though Goodreads is owned by Amazon. I've only been able to find apps that allow you to manually update reviews through csv, but that seems tedious when you have 600+ products or a goodreads html widget.
Anyone know how to better do this?
If you don't find an app or existing solution, I can build a custom app for you that pulls them regularly.
You could also hire a VA to grab them once a week or so then upload to your store if you don't find an app that does it.