A preview of Update 25 the Minas Morgul Expansion is now on Bullroarer. Note that they only keep it up for a day or so, this time until some time Friday. If you miss it, it may be up again before Update 25 launches.
If you have previously downloaded the Bullroarer client, it will update when you start it. You don't need to do anything special.
If you don't have a Bullroarer client, this tells you how to get one: https://www.lotro.com/forums/showthread.php?571061-Bullroarer-client-Installer-DOWNLOAD-LINKS The Bullroarer client is separate from your regular LOTRO client and should not affect it.
The Bullroarer server forum has more information about how to use it and resources available to make it easier to try things. https://www.lotro.com/forums/forumdisplay.php?787-Bullroarer-(Public-Test-Server)
You can copy one or more of your characters to Bullroarer so you don't have to start from scratch. You use the Transfer button on the server selection screen. Copies to Bullroarer are free. Your characters on Landroval are not affected by anything you do on Bullroarer. You cannot delete and copy your character again. At some point, the devs may wipe the server, which will allow/require you to copy your characters again.
Copying of shared storage does not work right now. [It was announced that copies from Landroval would stop working after maintenance on October 17, but they now say copies from Landroval will continue to work.]
The Black Book continues with Gandalf in Beorninghus. It sends you back to the Second Age.
Minas Morgul and the Morgul Vale starts east of Osgiliath (After the Battle).