The Vanguard series is a great concept, set in the same time frame as James Kirk and the original Star Trek, it's about a star base in the distant Taurus Reach, and its secret project, searching for the mysterious Shedai who once dominated the region, and trying to understand the unfathomable technology they left behind.
In this the fourth book in the series, the station's commander, Commodore Diego Reyes, stands accused of violating his orders by allowing the secrets of the station and its mission to be leaked to the media. The whole mission grows far more dangerous as Klingons enter the area, hoping to harness Shedai technology as weapons. In the background the nearby Tholians, once slaves to the Shedai, remain hostile, and powerful remnants of the Shedai have awakened.
A parallel story takes us to Vulcan, where there are ancient mysteries in the desert and a tie-in to Spock and an episode of the original Star Trek.
The nice thing about this volume in particular is that it brings in other elements from this time frame in the original series. The prologue and epilogue refer to Kirk's confrontation with Klingons and the peace imposed by the Organians. And one of the main researchers on the station is Dr. Carol Marcus, with her son by Kirk, David, still a child, but grown up in the film "The Wrath of Khan".
On the other hand one of the frustrating elements about placing a series of different adventures in a familiar time frame is the problem of where did it all go? There's very little here that shows up in other Star Trek, which makes sense because those stories were written first. But if the secrets of the Taurus Reach are so amazing, and the technology Carol Marcus is dealing with has such ability to change science, why are there no traces of it, no references to it, in the later Star Trek time frame? Apparently less than century later the mighty and dangerous Taurus Reach has become a backwater, too familiar and too tame to mention.
It's very possible that what Carol Marcus learns on Vanguard turns into the Genesis Project of "The Wrath of Khan". The Cestus III outpost mentioned in passing here, site of the original series confrontation between the Gorn and James Kirk, has in the time frame of "Deep Space Nine" turned into the only place in the galaxy where baseball is still played. But where's the rest of it? Were all the adventures we are reading about here for naught?
The other frustrating element is the enormous length of time between the publication dates of the books in the series. The previous volume was published almost two years before this book. When you have to wait that long, it's hard to keep track of who is who and what has happened, no matter how hard the author tries to fill in the missing information.
Fortunately the wait for the next volume won't be quite so long, as it's due out about half a year after this one. But one does wish Pocket Books could bunch up such an excellent series a little more, especially when each volume has such a cliff-hanger ending.