Short answer: This is better Exodus and Extremis but if you aren't even passingly familiar with the whole Starfire series, you're going to be really lost and probably disappointed. The whole series covers almost 500 years.
Middle Answer: read In Death Ground at a minimum first. Then Imperative.
Long answer: In 1977, Task Force Games published a little game of starship combat called Starfire, so small of a game that it came in a ziplock baggie. It was a huge hit. Fans and TFG kept adding to it and in the 1990s, David Weber of science fiction fame rewrote the rules AND made a truly wonderful scenario book called Stars at War, which reads like a novel (combining in depth narrative sections with scenarios) but you can actually play out the battles using the game system. This covered four different wars and the major races in the Starfire universe. Next came Crusade the scenario book and Crusade the novel, so if you didn't play the game you could read about space battles the old fashioned way...in a book. Then came In Death Ground and The Shiva Option, both novels, and the massive scenario book ISW-4 Arachnids. Then there is the orphan novel called "Insurrection" which had just the novel and not a game treatment. Then David Weber moves out of the picture and revised writing teams take over. This is where Exodus, Extremis, and Imperative slide into place as novels but no game treatment.
BaenBooks has reissued Crusade and In Death Ground as Stars at War One and Insurrection and Shiva Option as Stars at War 2. These are NOT the same Stars at War that David Weber wrote for Task Force Games back in the early 1990s.
The game system is now owned and supplied by Starfire Design Studios