Three or more topics that help the reader understand the book properly?We have to do an essay for english class on three or more topics.
A few ideas:
The biography of the writer.
The time period when a book was written.
How the book was published:
serialized, like Twain's work...Harriet Beecher Stowe's Uncle Tom's Cabin for example
self-published v traditional-published v ebook
Was the book translated? This can certainly have an effect.
More than one version, printing, edition, publishers, etc.
Has the book been censored?
All these characteristics contribute to the understanding of a book.
Hope this helps!