One of the incongruities in the text is the creation itself. For an uneducated, cobbled together “creature,” the creation speaks with a remarkably high linguistic ability. This is simply improbable, given his method of learning by proxy.
Consider this comment from chapter 15, when the old man learns about the creature.
Who can describe their horror and consternation on beholding me? (ch 15)
The monster always talks like this. He does sound like he was reared on poetry, but it does not seem likely that after the amount of time passed he’d be that proficient.
The monster describes Felix’s lessons, and how he listened and self-taught himself.
By great application, however, and after having remained during the space of several revolutions of the moon in my hovel, I discovered the names that were given to some of the most familiar objects of discourse .... (ch 12)
Although we can use suspension of disbelief and assume that Victor did a really great job putting his creation together, and the creation was a fast learner, it is still quite a stretch to accept that the monster would talk so eloquently, so quickly. He went from learning "fire, milk, bread, and wood" to using words like consternation. His words are like poetry, and they do add to the sense of other-worldliness about him, but it is still an incongruity.