Personally I never thought the Borg were that great an idea. There was very little you could do with them story-wise; they were more a force of nature than a personified antagonist. That's why the series shifted to telling stories about liberated drones, and introduced the Queen to give them a face and voice. The original concept was just too limited. If you want big space battles and action, then sure, you can use them for that, which is why they're still around in ST:O. But as a source of story
they're problematical. So they don't work as well in prose.
Recall that before the post-NEM TNG novels, the Borg were rarely seen in Trek Lit. The Borg were introduced on TV in 1989; Resistance
and Before Dishonor
were published in 2007. In between those, the only novels that really featured the Borg in a central role were Vendetta
, The Return
, and Engines of Destiny
. There were a couple of stories about finding Borg ruins (Mission: Gamma -- Lesser Evil
and Corps of Engineers: The Light
), and eleven out of the total 211 stories in Strange New Worlds
were Borg-related. Plus they made a cameo in The Siege
and were implicitly referenced in Probe
. That's three featured roles and a few sidebars in eighteen years. That's not a lot of prose. And there are reasons for that.