This is a copy of the only reference material allowed in the FE exam room. Review this book prior to the exam to become familiar with the charts, formulas, tables, and other reference information it provides.
This is the exact reference book you are given in the FE. Get to know it like the back of your hand, and you'll be that much ahead in solving problems quickly, especially problems not in your field of study that you can plug & chug if you know where to find the formula. Live with this book; eat, breathe, and sleep with this book. It is your new best friend, because this will help you when you forget everything else you studied in preparation. I cannot emphasize how important it is.
Don't buy the 6th Edition, get the newest one - 7th Edition, tan book. They are similar, but it will help you more to have a current copy. Like others have said, you can download it for free from NCEES, or buy it from NCEES for about $17 (with shipping, as of 2007). I prefer hardcopy, so you can get a feel for where things are.
(As a side note, for preparation materials I highly reccommend Lindeburg's "FE Review Manual: Rapid Preparation for the General Fundamentals of Engineering Exam" - very clear and concise coverage of the general FE topics, well written, good practice problems that I actually saw on the test when I took it.)
"You're gonna want this!"
Written By: John Weber
Yeah, you'll need this to study with. In fact, when doing any practice problems, practice only using this guide as your reference because that's the way it will be in the test. I sat next to some people during the test who clearly had never used it before and they seemed frustrated by the end of the day. I used it through all my practice problems and when test time came around, I had no problems navigating thought it quickly and efficiently.
"Required text"
Written By: T. Langdon
The text is difficult to follow but it must be used during the FE exam. It helps to be familiar with the contents prior to exam day. Well worth the cost.
"Too Expensive"
Written By: J. J. Moe
You can get this from the NCEES website for $8.95 or download it for free. Remember to do your research.
"Get this book to prepare for the Exam"
Written By: T. Lopez
I recently took the FE exam, and I have to say that it helped a lot. My recommendation is to use it, and only it, when solving practice problems. You will be glad you did!!