I just re-read the book that introduces Susan Silverman in Spenser's life. There are many nicely done bits surrounding their interaction, and if you start from the beginning (with The Goodwulf Manuscript; this is the second Spenser book) then you find a lot of freshness in his writing.

On the downside many of the plot points feel unrealistic, but once you enjoy the Spenser world then you happily ignore that.

Since almost all Robert Parker books are essentially the same (Spenser, or Spenser renamed as Jesse Stone, or Spenser as a woman, or Spenser as a gunslinger in the old west...) you will find this a fast read.