Ghost Ship seems too early, I'd say; there wasn't really a big change in novel feel when the first TNG books started, as far as I remember. They still felt largely the way TOS books did, just with a shift forward in setting.
If we're setting ages comic-style, it should probably go more by the overall tenor of the field; by that, I'd say you'd have the pre-Pocket age, the Rihannsu age (80s continuity and all that, picking the name because it's one of the more prominent parts even if it didn't actually start with the Rihannsu series), the [Arnold] age, the 90s age (I can't think of a good name for this, but the intermediary era when novelists started having fewer restrictions but interlocking works hadn't yet picked back up), and the Relaunch age.
edit: Arnold, not Maizlish