This article is from the Isaac Asimov FAQ, by Edward J. Seiler ejseiler@earthlink.net and John H. Jenkins jenkins@mac.com with numerous contributions by others.
There are actually three answers to this question.
A) Read them in the order of action, as listed by Asimov.
B) Read them in the order of publication.
There is no real reason why (A) or (B) is the better order. If you're
more interested in seeing the development of Asimov's universe, writing,
and ideas, you may prefer (B). If you are more interested in the course
of events in Asimov's universe, you may prefer (A). Note, also, that some
of the more recent books contain spoilers for some of the earlier ones, so
the impact of some stories may be lessened if you choose (A).
Note that Asimov in the Author's Note quoted does not actually suggest one
order over the other, but does suggest chronological order as a
possibility.
C) Just read the ones published in the 1950s (plus The Complete Robot ),
because the later ones all suck.
No true Asimov fan, of course, would agree that any of the Good Doctor's
books "suck," but there is pretty broad feeling that the later books are
not as good as the earlier ones. (There is also pretty broad disagreement
with this assessment.) In particular, Foundation and Earth is
considered one of the weaker books in the series. Of course, your mileage
will vary, and you may be one of those who prefers the later books over
the earlier ones.
 
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