Cradle of Monsters is a unique twist on the zombie horror. This time, it's on a cruise ship full of school kids coming back from a field trip. Next thing you know, the ship is filled with relentless murderers and the ship is capsizing.
Story - The story is very unique, with both zombies and a time limit to get outside the suspense is enormous. It can be quite gruelling when they go back for an annoying child or classmate, who is clearly dead or not fit to go on, when the boat is sinking around them and because of that get killed off, but I guess that's why its shounen not seinen.
Art - The art is certainly readable and it's not like the bodies are malformed, it's just that there's something off about Sanbei Kei's depiction of people, especially their faces. There is a fair amount of fan service.
Characters - Not only is there the school bully and his gang, there are those that were normal and nice turning evil and scheming. As the effects of the 'zombie bite' don't become clear for a while, it leaves plenty of time for evil scheming to get others infected, which is another point to the uniqueness of the manga. Highschool of the Dead may have had the evil teacher, but Cradle of Monsters has many evil living people.
Overall - I love zombie stuff so of course my opinion is biased, but I think it is a great manga and worth a read, read a few chapters before deciding it's not for you.