You can make your own army with Unholy tome V
and with elemental codex, you could blast every single enemy unit into the sky.
and with Unholy Tome you can create your own army of enemies and un-dead
like I said, you could blast all those units into the sky with elemental.
With Unholy Tome V is cheap and it can turn enemies into a weapon to defeat all
Here is how they are good in their own ways:
Unholy Tome V is good because you can summon skeletons, and raise dead, creating an army to fight for you. You can also cast poison-cloud on enemies.
Elemental Codex V is good because of shockwave, and you can use swap to uncover terrain exploits, and prevent being attacked.
Book of Life V is good because of Grow, enlarging your target, giving them more health and damage. It shrinks your enemies making them vulnerable to attacks.