So start your turn with this card, and after you Special Summon, then do your Normal Summon. "Book of Life" lets you Special Summon Zombie-Type monsters from your Graveyard. If you discard high LevelZombies from your hand for the costs of cards like "Magic Jammer", you can use "Book of Life" to Special Summon them to the field. But remember you cannot activate "Book of Life" unless your opponent has a monster in their Graveyard.