I read Ashes of Eden and was entertained and delighted by it. It could, arguable, be slotted in with the rest of canon without being classified as "shatnerverse." I have The Return, which I was always interested in because of The Borg, but always shied away from reading it because it brought Kirk back to life in The Next Generation's time.
That's the thing, is it is supposed to be The Next Generation's time. I do like that Gene Roddenberry held back from alluding to the original crew's fates, and it was nice over the course of TNG's run to get an answer for some of the original Enterprise's crew; a perfect little treat here and there in small doses.
I find it offputting when someone with enough ambition comes along with enough attention to detail to inventory all the old crew, and put them back into play in a setting that's so far removed from their prime place and time, when that setting belongs to a different ensemble.
I don't think I mind too much if the original crew presence is acknowledged in whatever place they've settled themselves into (Spock doing his reunification windmill, Scotty with his engineering thing, Uhura only hinted as residing in the shadows of Starfleet Intelligence). It gets weird when they are involved in the action. It gets wrong for me when two or more join up in an adventure.
So I was never going to venture much farther than The Return, and even that I might have ended up allocated to a bubble of apocrypha.