As expected, some Robert Parker fans are not happy two of his series are continuing beyond his death. A few have made the familiar comment that this is a publicity stunt that will tarnish Parker's legacy.
How is it anything but a compliment to one's legacy that others want it to live on? If Parker's legacy is tarnished at all, Parker did it himself by disregarding details in Spenser's background that, until then, had formed his history.
During Parker's life, it was said if he had only ended the Spenser series earlier, it would be even more renowned and better received than it is. As was his right, Parker not only continued Spenser, but created several subsequent series with dynamics similar to Spenser. Showing the same independent spirit, his estate has now allowed Ace Atkins and Michael Brandman to continue Spenser and Jesse Stone respectively.
In the end, I can say Parker was an eloquent writer who produced one of the steadiest P.I. series. I can't say it's the best, or that Parker had the brightest creative fire. His contemporaries Donald E. Westlake and Lawrence Block, for example, wrote several series that were tonally very different from each other.