Here are the Patch Notes for Update 18:
https://www.lotro.com/forums/showthread.php?608442-Update-18-Release-Notes&p=7570214#post7570214
There are some interesting items here: A new area; a new battle; some changes to the graphics (can be checked or unchecked in "Options"); a level cap raise; and some modifications to questing, festivals, and classes.
Two Dev Diaries:
The first one is an overview of Update 18.
https://www.lotro.com/en/u18
The Second one is on the Battle.
https://www.lotro.com/en/game/articles/making-battle
A Third Dev Diary was released today (4/13/16). This one is on Combat Changes.
https://www.lotro.com/en/game/articles/combat-changes
Enjoy!