There aren't many huge gaps, I don't just mean e.g. 'a year between A and B' I mean containing major major changes and even if they are they've been well covered in books, fan films and comics:
- Enterprise crew after Terra Prime (Star Trek: Horizon fan film closes one or two stories and there's the novel line)
- TOS Seasons 4-5, after the mission and maybe their 'origins' (various attempts in various media)
- New 5 year mission After TMP and before TWOK (comics/novels)
- Between The Undiscovered Country and TNG (Of Gods and Men/'The Lost Era' books)
- TNG pre-Encounter at Farpoint (novels, inc TNG Young Adult books Stargazer)
- Terok Nor (novel range)
- TNG crew between Generations and First Contact, debut of the Enterprise-E (Ship of the Line/Slings and Arrows)
Can anyone think of any more?
- Enterprise crew after Terra Prime (Star Trek: Horizon fan film closes one or two stories and there's the novel line)
- TOS Seasons 4-5, after the mission and maybe their 'origins' (various attempts in various media)
- New 5 year mission After TMP and before TWOK (comics/novels)
- Between The Undiscovered Country and TNG (Of Gods and Men/'The Lost Era' books)
- TNG pre-Encounter at Farpoint (novels, inc TNG Young Adult books Stargazer)
- Terok Nor (novel range)
- TNG crew between Generations and First Contact, debut of the Enterprise-E (Ship of the Line/Slings and Arrows)
Can anyone think of any more?