Katawa Shoujo can be described as a visual novel in which you date disabled girls, but that is an oversimplification. It raises multiple questions. What does it mean for two people to understand each other and fall each other? How can people overcome their own weaknesses, or change long-standing behavior patterns?
The characters you can date are quite well-written. While at first they appear to represent certain disabilities and certain types of people, but as you progress in their routes and learn of the aspects of themselves they hide from others, they come off as more easier to relate to, more human and more likeable. Their personal issues sometimes are related to their disabilities and sometimes are not, which nicely emphasizes that disabled people are people, too, not free of the problems everyone faces even while they have problems of their own.
Each route not only has a different kind of girl, but also a different kind of story and a different writer. As such, some may appeal to you more than others, based on the kind of girls or stories you like, but you should be able to find at least one that holds your interest, and may, by playing through them all, like one you otherwise would not have.
Hisao himself is a relatively interesting character, if not as much as the girls. After having his whole life turned upside down and leaving everything he knew behind, what direction will he take? The answer often depends on the girl he's with, and he often ends up drawing different insights about his life before as a result. The choices are often fairly interesting, in that you're often not asking him to respond to a situation, but where his priorities lie. For example, choosing whether to side with Lilly or Shizune is not as much about whom you want to choose, but deciding- is Hisao the kind of person who stands up for himself or takes things at his own pace? Such decisions shape Hisao's personality, and as such, who is right for him.
The art and music are quite well done, and effectively illustrate and complement the scenes throughout each route.
All in all, Katawa Shoujo is very enjoyable and insightful, and as such, is well worth your time.
My favorite routes are as follows: 1)Lilly 2)Shizune 3)Hanako 4)Emi 5)Rin, although to the game's credit, I did not dislike Rin's route, merely finding it less interesting than the others.