How to save iBooks before go back with Time Machine

MacBook Pro 15" Retina - OS X 10.11 (beta) - iBooks 1.3 (1060)

In recent days I have downloaded many iBooks, now I decided to bring back the whole system to a month ago with Time Machine, it is the first time I use this feature, my doubt is: if my Mac go back to one month ago, I lose all the iBooks?

If I understand correctly after this operation with Time Machine my Mac will be exactly as one month ago, without the iBooks, is true?

It is possible to save all the iBooks without having to reload from the Store or from the Cloud? Ie without generating internet traffic?

Are they stored somewhere in the system disk?

Thank you

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