There are some really neat themes in this that have been visited by Marvel in the past, like the idea that humanity shouldn't be meddling in affairs that aren't their business. Despite their being bred by Kree, the Inhumans are still of Earth. The same is true for Vulcan (aka Gabriel Summers, the brother of Havok and Cyclops) who married his way into Shi'ar royalty and murdered his way to the top. It's clear this intergalactic war is truly just between them, and they both face resistance from within, be it peaceful or violent.
That's truly where most of the "War of Kings" happens: on their own homefronts, as once again a Marvel book with the word "war" in the title has little actual war between its two principal factions. While there is violence and death (some of it gruesome,) the true battle is being fought politically. There are some great moments here in that regard, if you're a fan of these characters. The problem is, if you're not... I don't really see this as a story that will make you one. Does a former ruler being killed carry the same impact if you haven't seen her before? If a soldier who's had his head up his ass for decades finally snaps out of it, will you care if you hadn't been waiting it to happen for so long? Sadly, I don't think so.
If anything, this book may be guilty of asking too much of the reader. Even if you'd been reading Abnett and Lanning's cosmic work like "Annihilation" or "Guardians of the Galaxy" before this happened, there's a lot that's going to make you feel lost. However, if you're a big fan of the Inhumans (there aren't many) or followed the X-Men's dealings with the Shi'ar (those happened during some of their best stories ever, so that's reasonable), you'll likely quite a bit of enjoyment out of "War of Kings." It's definitely not for casual fans, but sometimes it's nice to find an event comic that caters to the longtime ones.