These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Magnum Opus: This is Lem's best-known and most well-regarded novel.
Nightmare Fuel: Burton's description of his vision over the Solaris ocean is pretty disturbing.
Moral Event Horizon: Chris crossed the line when he locks the first copy of Rheya in a pod and jettisons it.
Snow is actually dead, and his copy killed him in self-defense within thirty seconds of coming into existence, so copy Snow hid dead Snow in the ceiling.
They Changed It, Now It Sucks: Lem himself did not particularly care for this adaptation (though he didn't even watch it), citing concerns that it was too focused on the romantic aspects. But then again, he wasn't too fond of Tarkovsky's either.