it's an adaptive test. spend more time on the early questions making sure you get them right.
you score higher by getting a longer series of initial questions right than flipping right/wrong answers even if in both cases you answered the same number of questions correctly.
it's also a multiple choice test, use test taking techniques. ie: dont fret if you dont know the answer, look for obvious wrong answers to boost your percentages for guessing. if you can remove 2 answers, you're at a 1 of 3 or 1 of 2 chance of guessing right.
Simulate the testing condition with computerized practice tests so you get the feel for the software and sitting in one place for that long. review the content of the test but then get to taking practice tests.
i didnt bother buying any books. i went to the library and borrowed a bunch. the good ones even if i couldnt renew them, i just kept until the test date. i figured it was worth the 20 bucks in late return fees to avoid paying the 50 or 100 bucks the book cost by itself. got more practice questions that way.