My favorite by far is The Killer Angels. It's pretty much ALL history. But the entire book is the Battle of Gettysburg. That's it. Love it!! For only describing three days? (I don't really remember how long) the characters are incredible from both armies. I cried quite a bit. Some others that are YA and more story than history are:
Rifles for Watie
Across Five Aprils
Red Badge of Courage
I'll try to think of others, but that's what immediately came to mind.