You cannot activate “Book of Life” if there is no monster in the Graveyard to remove from play.
You cannot activate “Book of Life” if your opponent controls “Kycoo the Ghost Destroyer”.
If you activate “Book of Life” and your opponent chains “Call of the Haunted” to Special Summon “Kycoo the Ghost Destroyer”, you still get to Special Summon 1 Zombie with Book of Life’s effect (but do not remove 1 monster from your opponent’s Graveyard).