I read the Parasyte manga up to the point I am at the anime, so I'll get to read and watch the two versions simultaneously from now on.
The anime does a really faithful adaptation of the manga. However, a few things were altered:
- a few scenes were skipped in the anime (though, to be fair, they didn't really have relevance to the story overall)
- as the manga is around 20 years old, the setting was altered to reflect the current time (cleverly done, if I do say so myself)
- some characters had altered designs (some of them to better fit with the current time as well)
Overall, the story is largely the same, with all the important plot points and themes untouched. Props to studio Madhouse for the great adaptation.