The Dutch female Java developer community website jduchess has written up a review of Wicket in Action. They provide a nice summary per chapter detailing the contents of each, and conclude:
Wicket in Action is the perfect book if you want to get started with Wicket. [...] It’s also a good book if you’ve already been playing with the framework for a little while and want to really understand what it is you’re working with.
Many thanks go to Linda van der Pal for writing this detailed review!