The Expendable Few is the Spinward Fringe series, but book 6.5. It sits between book 6 and the forthcoming book 7. The author explained that he got a little sidetracked in writing book 7, and in trying to build more background for the story, he decided to release this as a separate book rather than an extremely long book 7.
The book starts out with a group of soliders (officers and enlisted) that have gotten into trouble with Freeground Intelligence. Apparently a puritan, fundamentalist group came to power in Freeground and it’s a much different place from what it was when Jacob Valance left with The First Light. All information about those initial missions is banned, and Commander Clark Patterson is arrested along with friends for having some.
He’s offered the chance to join intelligence, go on a mission to try and secure information about how to combat the Framework technology, and earn his way back into Freeground. Doctor Anderson is his group’s handler, and his mission to to retrieve one of the first scientists working on the Framework technology from an Issryrian world. He fails, and it killed, or so we think.
The book shifts to a second group that specializes in retrievals, and they manage to get a copy of Wheeler, one that’s a next generation Framework. They also combine with the remainder of the Patterson group and we slowly see some growth towards how this story fits in with the rest of the series.
It’s much different than the other books, and I didn’t love it, but it tackles the future world from another perspective, not the same shoot-em-up battle and high tech perspective of the other books. Good background, but definitely one you want to read after the first six.