In a graveyard, ghosts come alive at night. They converse and reminisce and socialize amongst each other as living people do. But the night the living boy wandered from his cradle to the graveyard, their world changed.
Nobody Owens, or Bod, lives and breathes among the dead. Safe in the graveyard from the man who killed his family, Bod is free to roam the graveyard as he pleases, and receives teaching from the resident ghosts. With each new adventure, Bod gets a little older and learns valuable lessons, usually after a spot of trouble.
The Graveyard Book consists of few chapters, but each chapters is its own short story. Bod has different adventures in each chapter, growing and learning and exploring his world and the worlds beyond (both among the living and the dead). But each chapter also ties into an overall storyline, weaving the adventures into the main plot and creating a bigger adventure out of several smaller ones. It's an interesting approach, and it can hold the attention of a reader with each new adventure, and learning how they all contribute to the main storyline.
Bod is an adorable protagonist. Starting off very young, he's curious and innocent about his world and the dangers that lie outside the graveyard walls. He scampers through the graveyard, meeting new ghosts and strange, very old beings. As he gets older, he matures and his curiosity grows. His guardian, Silas, is a protective father-figure and does his best to teach Bod. Silas himself is a fascinating character in that we know very little about him, and somehow it's alright. He's still a strong character even with his vague backstory and explanation of what exactly he is. It's good enough for Bod, and through Bod, it can be good enough for us.
The ghostly worldbuilding is fun to learn, too. Mr. Gaiman gives it to us simply, but there's an underlying layer of worldbuilding we don't know, and it enriches the worlds of the dead and their graveyards. Things ancient and things scary and dangerous lie beneath the earth. But we can sense there's a lot more behind what we're told, and while what we receive is satisfactory to the story, knowing there's more makes the world Bod lives in so much bigger and fleshed out.
The villains of this story are excellently frightening. They and how they connected to a part of the ending was a little confusing, but the enemy was scary and developed as deeply and richly as the graveyard, making them threatening and ominous.
Violence/Gore: It starts off with three murders (committed before the book starts). There is some "ghostly" violence, but it may be simply creepy to read (I don't think it would be unsettling, but the warning is here). A character is hurt and bleeding, and another falls into an open grave and breaks a bone. Three characters are thrust through a goblin gate (into an underworld inhabited by goblins). A scene near the end involving a villain and an ancient force may be a little unsettling for some readers.
Profanity: The D-word is used a couple times, but in an unrefined voice (so it may be not immediately recognizable as such). A small bit of referenced swearing.
Other: There are, naturally, ghosts and ghouls of the dead in this story, if you or your parents have concerns about this type of "genre." Since there are ghosts/ghouls and such, some parts may be a little unsettling for some readers. Bod also deals with bullying.