This being the very first book of the series, I felt that the story was more character building than it was a solid mystery. We were introduced to Rebus, the police detective with a horrible SAS past, and a semi-alcoholic. His ex-wifte and kid were introduced as well, however I felt that Sammy (his daughter) was portrayed as much older than she said she was. If they hadn't listed her age, I would have said she was 13 or 14, not 11. I hope Gill is around for the series, I liked her. But I don't remember her being in The Hanging Garden, which is book 7 or so of the series. And I wasn't too sure how I felt about the reporter. Half way between slimeball and decent human being.
As for the mystery, it wasn't too thrilling. One moment you don't know who it is, the next you do, without much buildup. But that wasn't the point of the book so it didn't make for a boring story.
It took me most of the book to figure out that naughts and crosses is the English name for tic tac toe :p