I've had this book for a while, but found it to be so far-reaching that I experienced trepidation about actually using it in a game. I just couldn't anticipate how my players might exploit it or use it to create custom spells that went far beyond what I could adjudicate on the fly. However, I've just found my first use for it, and it's great.
I needed a system for curses -- for people too weak to retaliate against aggressors through normal combat. And as I went looking for a good PDF, I remembered this book. The system for laying down a curse turns out to be wonderfully done. It empowers the weak without overpowering clerics & wizards (who are already powerful). However, clerics & wizards can certainly use the system. It's also great for how it cleverly puts a game mechanic behind all those curses you've read in fairy tales.
For example, I wanted a curse such as, "May your appearance be as ugly as your black heart!" And with that curse, I would hope the enemy would be disfigured or lose charisma or grow horns or... something bad. And it turns out that something open-ended like that is exactly right for this curse system. You figure out who it affects, how powerful of an effect you hope for, how long it should last, apply some modifiers, and poof, you have a curse.
My only issue with the curses is that they are listed as Necromancy spells, yet somehow commoners are supposed to be able to use them. Here is the paragraph in question: "Curses are easy to lay and difficult to remove. Elderly peasants who couldn’t manage a Ray of Frost can lay them. Dying men, offended parents, and anyone who’s wronged can lay them, even if they’ve never had any magical training." So... if curses are spells and commoners have no spellcasting ability, how's that work? If curses are a special exception, can commoners cast level 9 curse spells? If not, why not? Do they have daily limits as spellcasters do, or not? And what's their saving throw spell DC, considering commoners have no spellcasting stat?
In the end, that hardly bothered me. Curses have a level adjustment modifier if you let the curse eat a certain amount of your XP. So I just decided that commoners who cast curses have their XP eaten in order to get them up to the desired level. And I used charisma as their spellcasting stat.
I wish I knew how the author used curses, though. These issues must have come up.
Even with flaws, I really enjoy the mechanics for curses.
[4 of 5 Stars!]