The problem is hitting not only the game servers, but website services as well -- so be wary if you're thinking of going into your Turbine account right now. They have informed us that people are on-site at their data center and are trying to find a solution to the server problem. Also, there is currently no known time at which this problem will be fixed, but as soon as we have an update we'll be sure to let you know when everything is back to normal.
[UPDATE] Turbine has said that this is not caused by the Book 12 update, which was apparently successfully put onto the servers and tested by QA before these issues began. So when the servers finally do go back up, the update will be readily available.
[UPDATE 2] The servers are back up and it looks as though everything is now back to normal.