In English, the word in is used fairly commonly, as opposed to my native language. You can say sentences like The book is written in Esperanto. where in refers to the text's language (Esperanto). Google translator says it would be La libro estas skribita en esperanto. (I used translator because I just started learning. I mean, skribita as an adjective?)
On the other hand, in English it can also be used as in The cat is in the house. which means the cat is currently inside, similarly to La kato estas en la domo. However, it can also be used as The cat went in the house. which could be either La kato iris en la domo. or La kato eniris la domo. The second seems better, as it gives the direction, kinda like German with accusative/dative.
As a non European language speaker, can I expect to use always uses en where I would use in in English, or are there exceptions?