Those “Dominion War” 2-parters are odd - the TNG books are an original story, but the DS9 ones are adaptations of “Call to Arms” and “Sacrifice of Angels”.
There were a number of ‘event episode’ adaptations around that time, including the ‘Day of Honor’ ones for Voyager.
It does seem to be a specific niche of Treklit. I always saw it as a bit of a marketing stunt to draw in established fang to become new readers of the tie-in books.
I generally prefer original stories, and welcomed the Relaunch novelverse taking legacy characters and new ones forward.