Learn Italian: Leggo questo libro perché mi piace la storia. - I read this book because I like history.

The verb piacere literally means "to be pleasing to". So, instead of saying "I like history", you are actually saying "History is pleasing to me". The word mi means "to me", and piace is the "it is pleasing" part that matches the singular thing you are talking about, la storia (history).

Why is there a la before storia? In English we just say "I like history".

In Italian, when you talk about liking a broad category, subject, or concept (like history, sports, or music), you almost always must use a definite article (il, la, etc.). Because storia is a feminine singular noun, it takes la.

Why does leggo not have a subject pronoun like io in front of it?

In Italian, the ending of the verb usually tells you who is doing the action. The -o ending on leggo (from the verb leggere, to read) already means "I read". You only need to add io if you really want to emphasize that you are the one reading it, rather than someone else.

How do I know to use questo instead of another form of "this"?