Hi Yasaku, "on" is a preposition with diverse applications -- it can be used to describe LOCATION (The apple is ON the table.), it can be used to describe dependency (The man was ON drugs. / Babies depend ON on their mothers for sustenance. ), an event that is proceeding as planned (The train is ON schedule.), or in relation to a topic / subject being discussed (This book is on American history.) "About" is also used to refer to a topic or subject being discussed or thought of. In your sentence, you can also write "This is a wonderful book about American history." It depends on the sentence structure. For example: We say, "We are talking ABOUT you." and not "We are talking ON you." In this case, we talk "about" a person, not talk "on" a person. On the contrary, a writer writes "about/on" a topic. Hope this helps. Cheers, Lance

Yeah, you're right. When you're talking about the subject matter of a movie, a book, a class, etc., you can use "on" to mean "about". Examples: My sister watched a documentary on the animal kingdom. The professor taught a course on economics. I found a great book on Japanese in the library.

You can use "about" in this case as well. :)

"this is a wonderful book on american history" yes, the word "on" means "about" in this context. in english, the word "on" can apply to subjects and topics and ideas. so it can mean on top of a tangible thing, or it can mean on top of an intangible thing. examples of tangible things: "I am on the bridge" "I am on top of the roof" "I am on the plane" examples of intangible things: "my prediction is on point" "his project is on 'native american beliefs'" "her mind must be on something else" if this does not help you, let me know and i can rephrase it for you.