<p>I was interested in purchasing a PSAT book published by Kaplan, Princeton Review or Barrons. I noticed that prices are much cheaper on older editions of these books.</p>
<p>What exactly are the differences between the editions? Are the tests or contents different? If someone has the same book but two different editions of it by any chance, could you provide some specifics on the differences?</p>
<p>Thank you very much!</p>