With the demands of Unreal Development kit on the gaming market, there are lots of study materials found on the internet, some of them are really helpful and some of them are "OK". There are different stages of udk devss, the beginners, the intermediate and the expert. Well sometime an expert also need to refresh his minds with some basic foundations and standards, this is the reason why I liked a book which is newly launched by Packt Publishing and is authored by John P. Doran. I am reading it and I suggest other UDK developers should read, what is the outcome after finishing it is not my concern but till now lot of memories as a beginner were refreshed.
Link to the book : http://www.packtpub.com/mastering-udk-game-development/book