If I had to describe this book in one word it would be cute. That's right, cute. Number 13 has an endearing art style that makes all but the most bada-- of bada--es look adorable, from the genuinely cute moments to the ones that are meant to be serious, like going into a life or death situation. The bright colors do a lot to establish this tone, which to me comes across like a Saturday morning cartoon interpretation of a post-apocalyptic setting; it simply doesn't feel that dirty or grim. There is a wide-variety to the Fected introduced just in this first issue. A person can become anything once infected - no number of limbs is too low or high, any coloration imaginable is possible, wings, tentacles, tails, or becoming an amorphous blob - nothing is off limits here. The art makes full use of the unique qualities of its characters and does a lot to characterize them and establish that cute and innocent feel I've been talking about.
The background for the world is interesting, if undeveloped at the moment. I feel similarly about the characters and the main plot. There is a lot of cool imagery, but a ton of characters are introduced in this first issue, far too many to keep track of, and of them, only a handful of names are introduced and even fewer characters are given enough panels to give me an inkling of who they are beyond their physical appearance. The plot fairs a bit better in this book but doesn't endeavor to be anything unique to the genre despite the wacky options available.
Brightly colored, a little bizarre, and cute, Number 13 has the art to win over many fans but needs to slow down a bit and introduce its cast and unfold its plot before it throws too much at readers and loses the story in the process.