I liked it, all in all. It certainly had its flaws, it wasn't the most compelling reading ever (or even recently; I really enjoyed Redemption Rites), but all in all I liked it. I'm not sure about Gavin. I got the impression that he might be trying to stoke Erik's pride and ambition to fast-track the inevitable confrontation (and then stab him in the back when he overreaches); better to get him to overreach quickly then for the rivalry between Erik and Julian to burn slowly for years or decades. They should have left Alexander in captivity. He's more use to the Suns as a drain on Taurian resources.
Biut one thing really bothered me. This is going to get long, I'll try to remember to TL;DR it at the end. Three times in the book, the First Prince is described as the "first among equals". Twice in Julian's mind, once in Gavin's. One other time Erik demands Julian treat him as "one among equals, no more and no less." This is simply not the case. In the Five Princes Era, all five March Lords were Princes, that's why the First Prince is called the *First* Prince, sure. But Alexander Davion won the Davion Civil War in 2540, abolished two of the Marches, and replaced the heads of the other two, demoting them to Duke in the process. That was 600 years ago in universe. Let's look at how the March Lord dynasties got their seats:
Damien Hasek was appointed Duke of New Syrtis by First Prince Paull Davion II in 2829.
Raymond-Roger Marsin was appointed Duke of June and head of the newly-created Periphery March by Regent Yvonne Davion in 3079
House Sandoval is...less clear. The old House Davion Sourcebook says the Sandovals were Dukes of Robinson by the Davion Civil War, but the definitely weren't March Lords then, the book says they were supporters of the Rostov dynasty, who ruled the Terran March from Robinson (odd that the Rostovs weren't also Dukes of Robinson, but whatever). Tancredi IV was the capital of the Draconis March at the time, and it had a Prince named Vladimir Kerensky. No idea if he's related to Aleksandr et al. He apparently died without issue and was replaced by Alexander Davion's aunt Laura, who sided against her nephew in the DCW and lost. The first Sandoval we know by name (as far as I could find) is Vasily Sandoval, Duke of Robinson as of 2731. Not sure when they took over the March, but they have to have been appointed by a Davion First Prince during the Star League era (or immediately before, in the thin slice of time between the end of the DCW and FS joining the SL).
Edit: Handbook: House Davion says that the Sandovals "took control of the Draconis March in the wake of the Davion Civil War." So probably Alexander appointed them circa 2540.
All that to say, the March Lord families were all given their roles (and in two cases their Duchies) by Davion Princes (or a Regent, in Yvonne's case). The First Prince is not a Primus Inter Pares. The Prince appoints the March Lords, and can replace them if he or she needs to. It's really odd to me that all of a sudden the First Prince is thinking of himself an equal of the March Lords. I mean, it's "no one in power in the 3060s understood how regency or succession works" weird. Did Julian not learn basic civics in school? I guess maybe Gavin's been away most of his life, but he should've done some studying. Erik, I don't know, maybe he was too busy trying to help Aaron foment revolts in a FS ally to bother learning how the government works.
