Hey! Somebody unsolicited brings you some book/movie that means a lot to them. You should check it out. Often, unexpected blessings hide in ambush with things like that. If there are such blessings in "Valkyrie" they couldn't sneak up on Stevie Wonder.
In execution it's a pretty fine movie. Cast is competent, period details are precise, and all the explosions are believeable. I just can't figure out why anybody wanted to make such a movie, no matter how expertly.
It's an old problem in movie making. Tell a historical story where the outcome is already known. Generally what one does is spin off side stories. Sure, the ship is gonna sink, but here's these people here. Keep the audience guessing about their fate. "Valkyrie" doesn't give us a young German officer throwing his lot in with the conspirators while his pregnant wife frets. Nor does it give us some middle aged Chemistry teacher building the bomb, knowing if he's caught it could mean death for his wife and kids too. What it does give us is Tom Cruise in nearly every scene.
A good way to have gone with this movie, while still obeying whatever contract clause mandated Tom Cruise in nearly every scene? Explain what turned him against Hitler. That'd have been a very good film. Cruise/Von Stauffenberg could be schlepping around with his conspiracy to kill Manson, I mean Hitler, while it kept jumping back to his journey from goosestepper to patriotic assassin.
Tough stuff, these movies where the outcome's already known. Demands a deft touch. That said, well? The movie is historically accurate. Much of the moviegoing public don't even know there were high ranking Germans who tried to kill Adolf during the closing days of the war. It's good that folks find out about such stuff.