<p>I'm not sure how science/math/engineering textbooks differ from other disciplines, but in general, how many editions (or years) should you move back when purchasing used textbooks?</p>
<p>Personally, I don't think it matters that much. Science is not like other disciplines (government and politics, for example) where the subject changes a lot. An introductory text of physics, say, will cover the same stuff, since the things you learn in an intro class is basically unchanged for the past decades. So I'd say go back maybe a couple, till when you think the price is good for the quality.</p>
<p>i wouldnt go back more than two, but thats just me</p>
<p>The actual content usually doesn't change much, but the problems are going to be different. If you use an older textbook and are assigned problems out of it, find a friend with the newer one to get the problems.</p>
<p>International editions usually have the same exact content, but are paperback and printed on very thin paper, almost like newspaper print. If you aren't going to get the regular edition, I'd recommend those.</p>
<p>Unless its some cutting edge new field such as Nano-technology I feel its fine to buy older editions of textbooks (I mean how much has F= ma progressed in 4 years?) but keep in mind that the homework problems will be different.</p>
<p>Usually I borrow the current edition from a friend and then buy an older edition (dirt cheap too) for my personal reference.</p>