I would say that if what you do know, you know very well.... then you'll be fine. I would get the Lindeburg book. I took the FE in my senior year, but I was in a structural design program - which means that I didn't have any electrical classes, no traffic courses, no thermo classes, etc. All I really had was maths, physics, statics, dynamics, strength of materials, soils, and lots of structural courses, etc.
I had a couple blocks of answers that were all "C" when I got to the thermo and electrical questions. The afternoon civil portion only had (3) structural questions, so that didn't help much. There are many questions, however, that will be of the plug-n-chug type..... meaning all you have to do is find the equation in the manual and they give you all the variables, there are also things that apply accross disciplines (e.g. I used the principles of fluid mechanics to answer a traffic flow question). What I believe made the difference for me (because I lacked many of the classes that the test is predicated on) was that I knew really well what I did learn (maths, physics, strength of materials, etc.) and I feel like I got virtually every one of those questions right.