Star Trek: Seekers is a novel series from Pocket Books. Set in the Original Series era, the series follows on from the events of Star Trek: Vanguard, returning two of that series’ recurring starships to the Taurus Reach for an ongoing mission of exploration. Unlike Vanguard, the series does not follow a serialized storyline, but is more stand-alone in its approach.

http://memory-alpha.wikia.com/wiki/Star_Trek:_Seekers