Wasn't impressed by this series. The one thing most reviews say is that the magic system is very clever, and it is. But the problem lies more in that it's about the only thing that is clever.
The story itself is a straightforward adventure romp who gain magic power and end up together. The world described never struck me as interesting either. Every standard fantasy sentient appears (faeries, imps, goblins, fauns) with the only twist that these are all human, just with some racial differences (halfbreeds everywhere).
The ending of the series fell flat as well, because it continued on after they 'completed the quest' and turned into a 'will they get together or not?' story. Which is boring because you know from the first chapters in book 1 that the answer is going to be yes.
Entertaining in it's own way, but do not expect to be dazzled.