So, rather than attempt to review each of these books individually, I'm just going to give you my opinion of the whole series. Not that each of these books isn't worthy of it's own review, each is, I just know that if I try to make it harder for me to keep up this blog, it will never stay current. So, four books, one review.
Since I can't really tell you about the plots of all of the books without giving away spoilers for the earlier books, I'll just give an overall concept for the series. Megan Chase is half faery; her father is Oberon (yes, that Oberon) Summer King. Her little brother has been stolen and taken to faery, and Megan must go to save him. Meanwhile, the Iron Fey are taking over faery and slowly killing both Summer and Winter's lands.
I really liked this series. I loved the way that Kagawa wove known stories of faeries into this new tale. I loved all the Midsummer Night's Dream references, including Puck as Megan's best friend. (Probably because I love Midsummer Night's Dream so much) I thought the love triangle was believable, even though I was irritated that it was YET AGAIN a fantasy love triangle. I felt like Megan was an actor in her own story and definitely not passive. I also loved how Kagawa incorporated modern day into the world of faeries. It was an interesting take on a very old idea and I think it worked quite well.
These were definitely quick reads. I don't know that you would necessarily need to read Winter's Passage. It bridges the gap between the first and second book and follows Megan on a short journey. It was quite nice, and I liked the novella, but much of it was covered again at the beginning of the second book. If you like YA Fantasy or faeries at all, they are fun books to read!