IMHO, when you are reading a series, you always go in the order of the date of publication, even if some of the latter books are meant as "prequels."
http://en.wikipedia.org/wiki/Foundat...ation_Universe
But (again, IMHO) a bit percentage of "golden age" science fiction just has not aged very well, so you may not actually
like the material enough to try to read all of it.