I found that after adding books to Calibre, it get copied to Calibre folder in "Document". Therefore I have 2 book [one is original & other one saved in Calibre].
For example, I have book name "Apple" in D drive. Now I am going to add this in Calibre. I found this book in C drive under Document folder named as "Apple". Can I delete this book in D drive, since it is already present in C drive. If I do so, wil it be okay?