The Book of Shadows is the most powerful magical tome in existence. It belongs to the Warren line of witches and is over 300
years old. Created in 1693 by Melinda Warren
it has been passes down from generation to generation each Warren witch adding potions, spells, demons, and other supernatural things they run across. This makes the book extremely helpful to the Charmed ones. In the beginning the book was smaller than it currently is. This has even been reference by characters who've come from the past and saw the current book.
Though mostly used for information the Book is far from defenseless. Its powers include being able to sense evil, produce extremely powerful force shields around itself, Forces itself to remain in the manor, and has an empathic connection to the Charmed ones.
However its power is not infallible. The book can be corrupted by evil if the Charmed Ones are turned evil.
The book is well over 300 years old therefore it has a worn look to it and the pages are mostly made from parchments. However it does not become so aged that it fades or becomes unreadable. It may also have the ability to heal its pages. When Piper was on a demon hunt as a coping mechanism from Prue's death she used a marker to "X" out the demons pictures. However in later episodes the pictures were completely unfazed.
Connection to the afterlife
The book as a strong connection to the Warren witches that have moved on. As shown multiple times through out the show its pages can be magically moved by the telekinesis ( Penny
) from the afterlife.