I think there's more. I want to say that there's a Realm of Kings tpb with the one-shot that starts it off and the Son of Hulk mini (which is unnecessary really) and maybe something else. There's likely an Inhumans Realm of Kings mini as well. Then there's the Nova and Guardians of the Galaxy ongoing titles that had trades during the Realm of Kings era.
Then they all lead into the Thanos Imperative, which was great.
Did you just read the War of Kings trade including the main mini? If so then I highly recommend the other War of Kings trades including Nova, Guardians of the Galaxy, and whatever trade had the Darkhawk "Ascension" story (as well as the 2-issue Darkhawk mini that led into it).
Realm of Kings is collected into the following:
Realm of Kings which collects:
Realm of Kings one-shot, Realm of Kings: Inhumans 1-5, Son of Hulk 1-4 and Realm of Kings: Imperial Guard 1-5
Guardians of the Galaxy Vol. 4: Realm of Kings which collects:
ISBN (softcover) 0-7851-4049-2
Nova Vol. 6 ROK collecting:
The is an Imperial Guard TPB but it's included in the Realm of Kings HC.
I read Road to WOK, WOk:Warriors which had the Darkhawk storyline, and then of course WOK, I was going to go straight into The Thanos Imperitive but then realised there was some more story in between, is it worth reading is my main question?