neilfein (a user here) directed me to this diagram for a reading order.
It can be regarded as the absolute minimum of the books that need to be read for the series to be coherent and make sense.
Note that it leaves out a lot of short stories as it's trying to be concise.
Also this isn't chronological - it just tries to give you an overall understanding of the series when you so you can understand the back-story.
scifi.stackexchange.com/users/14317/Ender Delat
Most of Asimov's books are actually inter-related, but many of them weren't written with the intention of being related.
For example, the Foundation series was originally not intended to bear any relation to Asimov's Robots series, but he later decided to link them.
I won't go into specifics, for obvious spoiler reasons.
The best way to read Asimov stories is to read them in the chronological order of when he published them.
That includes short stories.
Since this is obviously very difficult, just doing what Deleteman says above is easily the best bet.
scifi.stackexchange.com/users/16534/James Sheridan
Apart from the Foundation and Robot series, Asimov's works aren't interrelated very strongly.
So apart from the Robots quadrilogy ( Caves of Steel , Naked Sun , Robots of Dawn and Robots and Empire ) and the Foundation series (original trilogy, two sequels, and two prequels) which should be read in order, there is little in the way of spoilers.
Though chronologically the Empire books do fit in nicely between Robots and Foundation.
Nemesis has also been retconned into the main continuity.
A rough timeline would be something like this: Susan Calvin Robot short stories (collected for the most in I Robot ).
Nemesis (Standalone book for the most part, but briefly mentioned in Forward the Foundation ) Caves of Steel (Robots quadrilogy) Naked Sun (Robots quadrilogy) Robots of Dawn (Robots quadrilogy) Robots and Empire (Robots quadrilogy)
The Stars Like Dust (Standalone Galactic Empire book)
The Currents of Space (Standalone Galactic Empire book) Pebble in the Sky
(Standalone Galactic Empire book)
Prelude to Foundation (Foundation prequel)
Forward
the Foundation (Foundation prequel) Foundation (Foundation trilogy) Foundation and Empire (Foundation trilogy) Second Foundation (Foundation trilogy) Foundation's Edge (Foundation sequel) Foundation and Earth (Foundation sequel)
Then there are the standalone Asimov science fiction stories that haven't been worked in any way into the Foundation continuity, chiefly The Gods
Themselves and the Lucky Starr books
(although the latter do mention the three laws of robotics and has off-Earth colonies that are hostile to the their mother planet).
scifi.stackexchange.com/users/887/System Down
I think you're pretty much safe regarding spoilers as long as you keep the order for specific series, like Foundation: you should not read "Second Foundation" before the first book, and so on.
But regarding the whole spectrum of him work (from the Robot series, going through the Galactic Empire and finishing on Foundation)
you're safe reading whatever order you want...
sometimes that might be fun, because you might find references to the same world but with thousands of years apart.
At least, that's been my experience.
scifi.stackexchange.com/users/3875/Deleteman
Years ago, okay, decades ago I read the books in the original three trilogies before the connecting books came out.
I recommend starting with the Elijah Bailey series (you can throw in I, Robot if you desire, but it's not necessary), followed by the Galactic Empire series, followed by the original Foundation trilogy.
The thought process behind this is that the Foundation was never even imagined to exist by the (fictional) humans through the first two trilogies.
After that, read the additional prequels and sequels in the order they were published.
It maximizes the "ah-ha" moments
and you're not reading a story that, in the fictional history sense, you already know some of the answers to.
scifi.stackexchange.com/users/43032/John
This question has been asked for the Foundation and the Robot series.. but I wanted to know if there are other works of Asimov that should be read in a particular order, so that I don't read the spoilers before reading the actual material.
What is the correct order for reading material of Isaac Asimov?
scifi.stackexchange.com
<suggested-order><isaac-asimov>
scifi.stackexchange.com/questions/39669
scifi.stackexchange.com/users/16795/Daud
 The best way to read Asimov stories is to read them in the chronological order of when he published them. However, apart from the Foundation and Robot series, Asimov's works are not particularly interrelated. Therefore, apart from the Robots quadrilogy (Caves of Steel,  Naked Sun,  Robots of Dawn and Robots and Empire ) and the Foundation series (original trilogy, two sequels, and two prequels) which should be read in order, there is little in the way of spoilers. Most of the writer’s books are not strongly inter-related. However, it is recommended the books be read in chronological order.
Most of the writer’s books are not strongly inter-related. It is recommended the books be read in chronological order.