In my opinion, the Shatnerverse books are Mary Sue fanfic written by someone who actually portrayed a beloved character. The Kirk in those stories makes Chuck Norris look like Tinkerbell. They're what a Michael Bay Star Trek movie would look like, if Bay had a hardon for William Shatner instead of the US military.
It's interesting that the only characters we seem to want from a Trek actor is the character he/she played. When did Nichelle Nichols write a Spock novel? Or George Takei do a Kirk comic? The only one I can think of is Walter Koenig writing an animated episode called "The Ultimate Vulcan."
The Shatnerverse novels were also aided by the writing of Judith and Garfield Reeves-Stevens. Sure, they centered on Kirk, but there was some good stuff mixed in throughout, IMHO.