Pros: Lots of fun.
Cons: Some may find parts a bit silly.
In the urban fantasy world of Monster, there are three types of people: incognizants, light cognizants, and cognizants. In incognizants, the part of the brain known as Merlin's lobe, which allows one to perceive magic, is underdeveloped, which means they can't see the magic and monsters that are all around them. Light cognizants can recognize magic when it's right in front of them, but once it's gone they have only a vague memory, which often gets rewritten into something more normal. Cognizants, as you can probably guess, are fully aware of all the weirdness running around.
Monster Dionysus is a cognizant who works for the Cryptobiological Containment and Rescue Services, the division of Animal Control in charge of capturing monsters who are causing trouble throughout the (unnamed) city. As a result of a run-in with a basilisk, Monster changes colors every time he wakes up, and each color gives him special abilities (or in some cases, weaknesses-he can't smell when he's purple, for instance). As if his life weren't strange and problematic enough, he's also dating a demon (think R. Crumb's Devil Girl) and the relationship is not exactly going well.
Monster first runs into Judy, a light incog, when a Yeti attacks the ice cream freezer at the grocery store where she works. Monster and his assistant, a paper gnome (a being from a higher dimension who inhabits a paper body on our plane) named Chester capture the yeti using rune magic. The next day they receive another call from Judy, whose apartment has been best by trolls. After saving her from monsters several more times, Monster discovers that Judy's tendency to attract strange critters is a side-effect of a destiny that puts her (and Monster) in the middle of mystical events with potential to change the world.
Monster is a light but very entertaining read. Though sometimes pulpy and even a bit goofy, Martinez does a great job of creating engaging characters and a believable world. The humor, action, and weirdness are mixed in perfect proportions and the story and characters are a lot of fun. The humor is a nice departure in a genre that often takes itself far too seriously.