Now and Then by Robert B. Parker

I've always loved the Spenser series by Robert Parker. (I have to admit that I haven't taken the plunge and tried any of his other series.) This newest one in the series lives up to its predecessors - snappy dialog, a plot that I can pretty much follow, and laughs along the way. Hawke, who was absent in the previous book, is back as Spenser's helpmate as they try to figure out why an FBI agent and his philandering wife were murdered. If you're looking for a quick read, this is the series for you - after carrying it around with me for a week, I managed to read almost all of it in a few hours on Thanksgiving Day!