See also 宮部 みゆき (Japanese language profile) and 宮部美幸 (Chinese language profile).
Miyuki Miyabe (宮部みゆき Miyabe Miyuki) is a popular contemporary Japanese author active in a number of genres including science fiction, mystery fiction, historical fiction, social commentary, and juvenile fiction. Miyabe started writing novels at the age of 23. She has been a prolific writer, publishing dozens of novels and winning many major literary prizes, including the Yamamoto Shūgorō Prize in 1993 for Kasha and the Naoki Prize in 1998 for Riyū [The Reason] (理由). A Japanese film adaptation of Riyû, directed by Nobuhiko Obayashi, was released in 2004.
"誰か" is another typical Miyuki Miyabe story: you have a mystery: here is the personal driver of the main's character father-in-law, who dies after being hit by a bicycle. His two daughters want to find the one behind the accident and decide to ask the father-in-love for help, the father-in-law telling his son-in-law to help the daughters. The main character having no other option but to follow orders. But..., was the death really an accident? Or was because of something from his dark past? And are out there more mysteries?
You also have lots of conversations, interspersed with the inner world of the main character, who helps to develop the plot by analyzing both conversations and plot developments. The psychology behind the characters, with reasons behind reasons, behaviors explained in detail and too many little details, conversations and actions that could have been cut out from the novel, also your typical Miyabe. And having as the main character a Japanese salaryman, even if he is one with family connections, also keeps with your 'normal people' characters as the center of Miyabe's stories.
And yes, you also have some twists and surprises that make things look quite different from what they looked like at the beginning. As, always, the book is easy to read, it is fun, it is filled with pointless stuff and it leaves the feeling that, with a little bit of tweak here and there, could have been something special. But, being an interesting and fun read is more than enough.
The best: it is your typical Miyuki Miyabe
The worst: it is your typical Miyuki Miyabe
Alternatives: read the long "ソロモンの偽証"'s series, by Miyabe herself; or you can read Edogawa, Kirino, Yokomizo, Nishimura, Higashino, Akimitsu Takagi... the list is endless, but Miyabe is more interested in the characters than in the mystery