Another solid entry in what's been a very dependable, well-written series. The mystery itself was a little predictable, but I can't be certain the author didn't intend that, as the clues weren't subtle; a story about PIs wouldn't really work with subtle and still be fair to the readers.
There's some character development in this one, as well as references to a previous plot that make this less than ideal as a standalone, and it's wroth the time to start at the beginning with book 1.