The standard books, like King's and Henderson are good references to have in general, but I did not use them too much.
In preparing for the test, I found having a Civil Engineering Handbook (of which there are several) was useful, and the Lindeberg books, especially the sample problems books and the guide, were very useful, as they got you used to the type of problems you will encounter in the test. They have several different ones, one was very representative of the test, and the other was overkill.
I found it was more important to have a good grasp of fundamental concepts, you should be able to say discuss the difference between super and sub critical flow, and be able to use practical things like monographs. I found them useful for a quick double check or to get started towards the right answer.
helped my confidence factor, their goal is to sell you books and services (I got my books from them, but not the services), but they also have a lot of pages with useful advice and people commenting on their experience. Just remember, though, the test people can always through you a curve ball. The main thing is to go in with the right mindset, and also to know what just what the heck Hazen Williams is
