I've nearly finished To Kill a Mockingbird and I've really enjoyed it. I love how the main events have been shown from an 'outside perspective' i.e. news coming second hand from a biased character, or witnessed by Scout/Jem unknowingly by their Father. Perhaps the scariest thing is that these events don't seem all that far-fetched or shocking today...
I'm really glad to hear you enjoyed Old Man's War! Will you be reading the second one? I'll give it a go in the next few months hopefully (though there are some other books I want to read first to help with the bingo).