I was surprised, frankly, that Shiver was a series book. I'm not sure it really needed to be. But Maggie Stiefvater is great writer, each page just busting out all over with poetic phrasing, so I suppose it doesn't hurt to tack on a few more.
The four POV characters were great, I particularly liked Cole then Isabel. I found them much more compelling than Sam and Grace in this foray, mainly because they have more movement in this work as Sam and Grace pine and fret, fret and pine.
I loved the wolf parts, and again the writing was gorgeous, but this took me some willpower to get through - but I've never been a big fan of teen romance even when I was a teen (particularly the 'let's get underage married right now and I'll bake for you forever' kind), so I am not sure that this is the books fault - just my own preferences.