Book of Evil

[Namel]

Is book of evil any good?

I did quick test with it and not really sure if it is worth casting instead of another fireball. Of course my test ended up really bad when I used book of evil against last mob alive, killed it and then chain lightning hit 5 of my own units killing ten times more units than I ever had lost in that battle even if I had not cast single spell. Unpredictability might be big problem with it.