Can you use the word not twice in the same sentence?

It is not a grammatical problem to use the same work twice (or more) in a sentence. However, it is often poor style and can be more difficult to read.

For example:

"Of all the books I read this month, the book by John Smith was the best economics book."

There are no grammar violations in using the Word book three times. However, a more pleasing version is as follows:

"Of all the books I read this month, the one by John Smith was the best economics text."