I've loved this series from the first book for many reasons:
First, Holly Black's works have never failed to entertain and astound me (and after reading this series, it's hard to imagine she ever wrote about fairies- which I equally enjoyed).
Secondly, this series reaches that level of cleverness and suspense that I could only ever dream of achieving. I can't imagine the work that was put into making sure the tiniest detail had meaning, and tying it all together in the end for one heck of a thrill ride.
Most of all, I adore the character of Cassel more than any other YA male protagonist. Not only did the complex events surrounding his life influence him in unique ways, but his entire attitude toward it all- so honest and frank hyperaware of all of the obstacles barring him from a normal life- made him believable and endearing.
This is not to say the other characters weren't interesting: I can't think of a single side character that didn't stand out in their own way. No one was a wall flower, and no one was without a purpose: it takes careful planning to pull that off well.
I won't get into the details of this last installment- anyone who has gotten this far and stuck with the series for this long already knows how awesome it is. I think this is possibly my favourite book of the three, which surprises me, since I'm one to take to first installments. The events in this book that lead to the ending are fast-paced, intense, and keep you guessing all the time. I was never sure of what was going to happen next, and for a story like this, making sure the reader is always on their toes is important.
I could go on and on about this, but I have to stop somewhere. This was a great ending to a fantastic series.