This is a classical whodunnit, dun right.
We're introduced to all the characters fairly early, so there's no sudden introduction of the killer 90% of the way through the book. Everything follows logically, without outrageous coincidence (as detective Beaumont says, the police don't believe in coincidences, so why should mystery readers be expected to), and naturally, I didn't figure out whodidit, even with all the clues.
I must say though that it was terribly dated - this library e-book had a copyright date of 2005, but the DTB was published in 1989. Nobody has cell-phones (Beaumont has a car phone), everybody apparently uses actual answering machines, and computer technology is primitive. How did we ever manage?