"Increase the XP of your harem to improve their battle stats"
Books grant experience to your Harem guys to raise their level and stats. Each guy's level will cap at your account's current level. If you give more exp than required to hit the current cap, it will only carry over enough to get up to 1 less than it will take to reach the next level.
Books come in 4 types across all rarities. All 4 rarities can be purchased in the shop or won in Pachinko. Epic grade books will only appear in the shop after you reach level 81. Legendary will start to appear at level 201.
Magazine
Common grants +4xp and costs 801 cash.
Rare grants +80xp and costs 16,022 cash.
Epic grants +180xp and costs 36,050 cash.
Legendary grants +1,000xp and costs 200,000 cash.
Book
Common grants +9xp and costs 1,803 cash.
Rare grants +100xp and costs 20,028 cash.
Epic grants +200xp and costs 40,056 cash.
Legendary grants +1,500xp and costs 300,000 cash.
Encyclopedia
Common grants +20xp and costs 4,006 cash.
Rare grants +120xp and costs 24,034 cash.
Epic grants +250xp and costs 50,070 cash.
Legendary grants +2,000xp and costs 400,000 cash.
Spell Book
Common grants +40xp and costs 8,011 cash.
Rare grants +140xp and costs 28,039 cash.
Epic grants +500xp and costs 100,140 cash.
Legendary grants +2,500xp and costs 500,000 cash.