"Koray" wrote

My father is writing a book. He has selected the whole
document and deleted.
After that he saved the document. How can i recover the
document.

If he only saved once, the {filename}.wbk file should be OK.
Immediately make a copy of it and save it in a safe place.
Make another copy and rename it {filename}.doc or whatever
extension the file he was working with had.

My wife did exactly what your father did except that she
went to the trouble of saving the file twice, which of
course trashed the backup.

A tip: I disabled the control-A shortcut to select the whole
document on her setup of Word. You might consider doing the
same thing.

Another tip: Every morning after she's worked on her book
(she works at night) I copy the file and its backup to a
separate directory on a USB drive attached to her system.

--
Bob

Kanyak's Doghouse
http://www.kanyak.com