I have been using struts for about 2 years and the best advice that I can give is to grab a tutorial online and develop something small. If you do that, you will be able to see how everything fits together, actions, forms,
jsp's etc. Then once you have a decent understanding, get a good struts book, it will make it easier to understand.
I started with the book and found it very confusing, so I just jumped in. I admit there wasn't very much good information back then to consult, the best resources were user groups. I am sure the books have gotten a lot better but the best way to learn is hands on.