As others have stated, Streep's acting is good - the movie is not. It tries to trick you into thinking it's in any way meaningful by liberally throwing around subjects like death, suicide and concentration camps, but at it's heart it's an unengaging story of a love triangle that is played out way too long and to no effect together with the underlying theme of a coming of age story of Stingo
which, ludicrously enough, is concluded by him losing his virginity to the older woman, who then leaves him a note in which she repeatedly tells him what an amazing lover he is....
The worst offense though is the part about Sophie's "choice"; it's historically ridiculous in it's portrayal of the Nazis. The whole scene is a shameless tearjerker that tries to one-up the Nazis, as if what they actually did in Poland and elsewhere wasn't bad or drammatic enough to make a film about.
I can't judge to what extend the book is artistically relevant in it's attempt to rewrite the history of Nazi's crimes in Poland as not having been mainly against Jews but a manifestation of a higher Evil directed towards all humanity and to have those views reflected in modern society - but when you just look at this film adaptation, you'll hardly have to bother with such nuances.