Re: To be interested 'in' sth
Hello hashamyim and welcome to our forum
There is neither accusative, nor preposition involved because you could say that the structure is more like this (translated word by word): "something interests him".
So the "something" (alias "in something" in English) is really the subject of the sentence.
Ez érdekel. - I am interested in this. (This tickles my fancy - if you wanted a structure closer in English and if the context allows it.)
Mi érdekel (ebben)? - What do you find interesting (in this)? (Just to illustrate that "in" could be involved but only in its usual meaning.)
Nem az mutat tudósságot, aki sok nyelven beszél, hanem aki hasznos dolgokat tud mondani rajtuk. (Comenius)