Gorey's specialty is writing horrific stories about the bad things that happen to unfortunate children. His books seem designed to give little kids nightmares, and I have a hunch that they are often successful. They are sick, deadpan, mean-spirited and often hilarious. This is one of my very favorites.
'Tis the story of a young child who has a tragic and very brief life, every page packing on another misery for the little tyke to deal with, culminating in the child's unceremonious and highly ironic death. Death, abuse, sickness, fear and suffering are the major ingredients of the child's life, and the story is brought to life through Gorey's marvellous illustrations. I'm not giving any of the details because that would just take the fun out of it.
This is one of my very favorite Gorey books and would be a good starting place for someone new to him. But, if you don't like your humor black as the blackest black that ever blacked, perhaps "The Gashlycrumb Tinies" would be a better starting place: it's more overtly funny, while this one has such a tragic end that you have to be pretty twisted to laugh at it. That didn't stop me, of course.