There are very few reviews for Attack on Titan yet, because I think Kodansha (being Kodansha) didn't send out that many advance review copies. Some of the reviews listed below are written by people who either read the series in Japanese or read pirated scans of it, but here you go:
Also, I would advise against googling "Attack on Titan review" right now because the very first result that I got had a HUGE spoiler for a genuinely shocking twist that comes later in the series, right there in the title of the link, argh.
no subject
http://elitecosplay.com/attack-on-titan-manga-review/
http://wtf-film.com/site/2011/06/01/shingeki-no-kyojin-attack-on-titan/
http://animeshinbun.com/news/1015923/shingeki-no-kyojin-review-titan-killing-has-never-been-more-fun-anime-aura
http://www.bateszi.me/tag/attack-on-titan/ (2 really great posts here)
Also, I would advise against googling "Attack on Titan review" right now because the very first result that I got had a HUGE spoiler for a genuinely shocking twist that comes later in the series, right there in the title of the link, argh.