I'm going to kind of stick with (more or less) what I said in my review on this book's Amazon page. Let me preface this review with the following:
I hate 99% of zombie-related anything. About the only time I've really been able to tolerate zombies has been 7 Days to Die (because I can play with my friends) and AD&D (because zombies are created by magic). Otherwise, the genre drives me up the wall for a variety of reasons. Honestly, I probably wouldn't have bothered had I not interacted with the author online a few times. At which point, I figured, "what the heck? I'll give it a shot."
Alone Together has a completely different feel from zombie movies, games, or literature I've encountered. It starts with science gone bad, of course. (How else could you get zombies without someone, somewhere tinkering with forces of nature they shouldn't.) S.S. Fitzgerald, however, builds a chain of main events and series of side-events that makes one realize that (1) there is way more going on here, (2) these aren't ordinary "it's a virus" zombies, and (3) yeah, this is actually something that is trouble. Most of all, it let me suspend disbelief and read the book without my wife wondering why I'm ranting about something called adenosine triphosphate. In fact, I'm not sure I would even call the (formerly human) creatures in Alone Together zombies in the classic sense.
Alone Together also brings a perspective and human element to the mix. Fitzgerald does an excellent job capturing the mix of emotions among the protagonists from raw terror to stalwart acceptance of a bad situation. At no point in the book, for example, was I really left in a position of asking myself, "why in the blazes would these people do something so colossally stupid?" And, at no point am I really left going, "gee, I don't think it makes any sense for someone to react that way, given what just happened to them." The characters' reactions to the situations, good and bad, make sense.
S.S. Fitzgerald has, I think, done a great job at bringing multiple protagonists with different backgrounds together while portraying their different reactions to a terrible situation in a believable manner. He's done a great job creating a believable cast of characters, a horrifying yet believable chain of events, and a zombie-like apocalypse world that doesn't make my head want to become one with the surface of my desk.
I can't wait to see what he does with the sequel.