The latest 12th edition is a staggering $186, but there are older versions of the reference manual that they are practically giving away. Has anyone reviewed both copies? Physics hasn't changed a lot over the last couple of years, you'd think the old one would be good enough, but I could be wrong. I'm still a few years off from taking the test but I want to start learning the stuff now. If having the latest edition is really that important, I don't want to risk spending that kind of money on the 12th if the 13th is going to come out a year or two from now before I actually take the test. But, on the other hand, I don't want to start studying out of the 8th edition only to get the 12th or 13th later because I'm better off being familiar with one book that I take in to the test with me.