The good news is: the more David Levithan I read, the more I adore him.
The bad news is: the more John Green I read, the less I enjoy him.
This book pretty much cemented my impressions on both of their writing styles, for better or worse.
Both Will Greyson's come from a place of internally constructed isolation, both for similar reasons. The way they go about isolating themselves takes differing forms. Levithan's Greyson is so filled with self hate that it leaks out of him onto everyone else. He's not a likable person, but he is a realistic and well crafted character. My heart broke for him repeatedly, and in my own way I could relate to him. His sections are painful to read they are so raw.
Green's Grayson follows a set of rules that keep him distanced from people around him in an effort to avoid being hurt, which of course leads to him being hurt. While I found his character arc more satisfying I also found it more trite. There was that affected tint to Green's sections that made everything ever so Hip and Quirky. The writing felt more concerned with being cool than with being honest. It was the same tone I found so irritatingly precious in Paper Towns. (I dislike movies like this too, for the record. I'd say Wes Anderson fills a similar space in film, if that gives you an idea.)
This is all a roundabout way of saying that I really liked 50% of this book, and I was rather ambivalent on the other 50%. There is a lot of great stuff in here. The issue of cat fishing is dealt with so well it actually made me cry. There are some brilliant scenes and remarkable characters. And the way things fold together and then pull apart is very well done. The ending was a bit lacking for me, but I did appreciate what it was doing, and I'm not certain what might have made it more emotionally satisfying. Overall I found this book a worthy read, and a good introduction to both authors.