how can delete book from ibooks completely?

I have a problem with iBooks that I download a book from iBook but I cant remove a totally the source of this book. how can solve this problem? ----------------------------------- I edit this text because I didn't write about the device to delete from. my device is MacBook Pro and I like to delete source of a file in types .epub from my iBooks but I cant do this and after removing the file from iBooks the book it's there and I just can hide it!