One thing that really helped me was to create a 3-ring notebook of all the problems I had completed. Look at the exam format (breadth and depth) and make sure that you have an example for each topic listed; maybe one notebook for the morning and one for the afternoon. This really helps to see...
If you are going to purchase one wait until the last minute so you can return it once the test is over. I really was only able to find one answer in the dictionary. I'd say it's worth getting, but don't waste your money on an expensive book.
Don't they reset the accounts each exam? I think when you register it's only valid for that one exam. I took the test twice and had to set up two accounts; one each time. Maybe they have already reset it for the April registration period.
NCEES will never divulge passing rates, but it is typically high 50's for Civils. You'll get it next time... change your study habits and try and get in a review course if available. PPI also has some good products out although I have only used their Civil products.