No, there really is more than just yaoi hints. First manga is the big introduction of the characters, the setting and the possibilities. Lots of hints. One big hint probably. But in the second volume there is the Madame Red case already and that is so much deeper than yaoi. It's so awesome, even if you would have seriously ugly characters in their place! There are so many awesome stories in it that are fun to read, even if Sebastian wouldn't be carrying Ciel around!