Books with a character who is alone most of the time?

I recently read "I am Legend" and i think beyond the cool premise, the biggest thing i loved is the loneliness of the main character and how he copes.

So i would like to read more of the type, though preferably it would be something with more…action. Not just the character cooped up in a box. ( Tho i did like that aspect of I am Legend a lot)