This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
I think ZK has a pretty good documentation. So that's the best place to start. You need to try out sample applications as you read along. (I dont think there's any other material (books) avaialable for ZK framework)