I won this last Friday and have had it equiped since. My main interest was the stats and resists so I'm quite happy.
Supposedly this causes you to cast at 20 levels higher (85 in my case) and reduces the fizzle rate. My fizzle rate is the same and if anything seems worse the last few days. Probably because I'm actually paying attention to it. Perhaps the effect is more subtle than I can detect.
In any event this is a nice "Book on a stick" item, but I wouldn't go out of my way to get it if your interest is in the effect and not the stats.