Given how spread out some of the characters are (Bashir in Zero Sum Game, for instance) I just classify them along with Articles Of The Federation, Destiny, A Singular Destiny, and the forthcoming Indistinguishable From Magic as a sort of "shared novel continuity" that doesn't belong to any particular series. That seems to be the way they're branded, anyway; "Star Trek" and nothing else.
From what I gather, Indistinguishable
is more of a TNG novel with guest stars, though I'm not sure how it's being branded. Now, my DTI novel is definitely not attached to any specific series, and in fact has some overlap with all of them (to varying extents).