"A book on...", "A book about..." or both?
The first variation is from a grammar book I learn English with. I just saw the word "a book", the preposition "on" and "Mozart's life" combined, but I'm not completely sure if it's the same as if it says "A book about Mozart's life". Give me a hint please.

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Answer

We use 'on' for non-fiction, schoolbooks and academic texts. If you say "a book on electronics", for example, this is the subject of the book.  We also use on for the subject of lectures, documentaries and so on.

We can use 'about' for any type of book.  While you can say either "a book on electronics" or "a book about electronics", we use only 'about' for non-fiction: for example "a book about a little girl who flew to the moon".  We wouldn't use 'on' for the subject of a storybook.

Answer

Both denotations express having (something) as a topic.