I bought this several weeks ago and I've been biting chunks out of it whenever I've felt the jones for Treklit or scifi in general. As you can tell from the cover, the book is set during the TOS-era, before the movies. Here's the synopsis from the book itself:
Located in an area of non-aligned space near Federation and Romulan territory, the Kondaii system is home to a unique stellar phenomenon: a spatial rift that opens every three years in proximity to the system's sole inhabited planet. Only during this brief period is communication possible with the small, mineral-rich planetoid inside the rift. The local population has established a mining colony on this planetoid, and for the limited duration that the rift is open, a massive interplanetary operation is set into motion: ferrying mineral ore to the home planet while simultaneously transferring personnel and replenishing essential supplies and equipment–everything necessary to sustain the colony before it once again enters forced isolation.
While studying the rift, the science vessel U.S.S. Huang Zhong is severely damaged and crash-lands on the planetoid. After the Starship Enterprise arrives to conduct rescue operations, evidence quickly points to the rift's artificial nature. It is a feat far beyond the capacity of the local inhabitants, and presents an alluring mystery for Captain James T. Kirk and his crew. It also attracts the attention of the Romulans, who are most interested in studying and perhaps seizing this supposed advanced technology–by any means necessary.
I like it so far, it reads like an episode of Star Trek and there's a connection to a classic episode of TOS - one of the characters is
Samuel Boma, who was a science officer in
The Galileo Seven. There's a bit of discontinuity here between That Which Divides and two novels by Diane Carey: Dreadnought! and Battlestations! In those, Boma is said to have been court-martialed by Scotty and kicked out of Starfleet for his actions during that episode. Afterwards, he went to work as a civilian scientist where he created a new type of alloy and worked on developing new weapons. Fortunately, it's not a big deal.
Assessment so far: A good read. I'd recommend it if you like Treklit or are looking for a good place to start. The book is standalone, so you don't have to know any of the continuity that the Treklit has built up.