Natsume can see and talk to yokai (spirits, essentially) that nobody else can see, which makes him seem odd. He isn't terribly surprised to discover that he's not the first person in his family to have this ability. His grandmother could do the same, and bullied the yokai around her by using her strong magical talents to trap their names in a book, the oddly named book of friends from the title. When Natsume discovers the book, he decides to free the spirits trapped in the book by giving their names back.
There's the basic setup, which sounded fairly interesting to me. The execution is even better. Midorikawa gives the yokai varied, intersting, and often sympathetic characterizations. The chapters are somewhat longer than I normally see in a manga (there's only four in this volume) which allows for the situations and guest characters to be given greater depth. The last story in this volume, about the spirit of a sparrow, is sweet and touching. Because Midorikawa wrote each chapter as though it could be the last, there's closure at the end of each story, while leaving Natsume's story open for more.
The art's great, too. The human characters aren't drawn too similarly, and the yokai designs have some good variation, while still looking like they all belong to the same world. I'm especially fond of Natsume's design, and how the way he's drawn subtly conveys his loneliness and exhaustion. (Releasing the names from the book of friends takes a lot of energy.)
I will absolutely be continuing in this series, and I think it has the potential to become a favorite of mine.