Mary I always prefer to read a series in order, but it isn't necessary in order to enjoy the book. It will, however, be something of a spoiler if you decide to go backwards and read other books in the series. This series is somewhat unique in that there are five or six characters, including Lynley, that dominate the series. Different books concentrate on developing their life stories and deepening their personalities. I would recommend starting with the first book, and seeing whether you are interested in reading the rest of the series.