You mean, aside from the D&D 5E Monster Manual and DM's Guide, so I could see how the game really works? I'll tell you what I'm more excited about...
The Valiant Universe RPG
I know you can get the pdf already from DriveThruRPG, but I want the book in my hand. Why do I want this game?
1. It's a superhero RPG, and I loves me superhero RPG's.
2. It's based on Valiant Comics. They got going in the early 1990's and ran for a while before folding their tents. Then they re-launched all the titles in 2012 and have been rolling along ever since. Valiant's comic book universe has a lot going for it as the basis of an RPG. The comics are pretty gritty with murky, gray morality. Most of the characters are pretty low-powered as superheroes go, so no wildly over-the-top stuff. Third, and perhaps most interestingly, when a character in a Valiant comic book dies, they stay dead. The publisher is pretty explicit about that. Recently one of the characters from their flagship title Harbingers died and it was a major moment in the book because you knew that one month or six months or ten years later she won't be returning.
3. The rules look good. There's been several free preview pdf's out there that are all the same in terms of rules content, but feature different characters from the Valiant universe. The rules look a lot like Marvel Heroic Roleplaying, but without some of the dice-wonkiness (but only some). It doesn't look like you can have the fluke one-hit-KO's you can get in MHR, which while I think I are appropriate for the genre, tend to piss off players when they are on the receiving end.
What I haven't seen, and I think might make-or-break the game for me, is the rules for making your own PC's. For all my obvious fan-boy love for Valiant, I like making my own universes for my RPG's rather than use someone else's, and I especially don't like it when the players have to use pre-gen PC's. If the Valiant RPG uses they same "rules" as MHR for PC creation, namely "just make up whatever the GM will allow" I might end up shelving this thing.