Frankenstein opens with a warning that the film is super-shocking, run, hide your children, be very afraid. Actor Edward Van Sloan says, in an opening preamble:
It may shock you. It might even horrify you. So if any of you feel that you do not care to subject your nerves to such a chain, now is your chance…
So should you be afraid and hide your children? Well, the truth is that by modern standards, Frankenstein isn't all that shocking. There are a couple of murders, including one of a child, but none of them are gory and graphic; you can see worse on television or YouTube without even trying.
And of course there's virtually no sex beyond a chaste kiss or two. The film is innocent that it thinks you make new life by electrifying dead body parts.
But while the film isn't very shocking today, it definitely was at the time. As a result, some versions were censored. In particular, a number of state censor boards cut the part where the monster throws Maria in the lake to drown. They also cut out the part where Frankenstein says:
Oh, in the name of God! Now I know what it feels like to be God!
Humans weren't supposed to claim to be God in the 1930's, even if they later get punished for it.
When the film was rereleased after 1934, the Hayes censorship production code had come into full effect, and all versions of the film had these bits excised. As the film has come to be seen as a classic, though, those clips have been put back in, and any version you see now should be fully, completely, totally as shocking as it should be.
(Which, as we've said, isn't actually all that shocking. But still.)