My favorite right now would be John Steinbeck's "Grapes of Wrath". I read this book a few years ago, but I reread it recently and it was just as good as when I first read it.

John Steinbeck is amazing when it comes to creating characters, in his books he describes them so well that you feel like you actually know the character. It definitely gives you a better connection with these characters so you can empathize much easier.
This book is about struggle in general. It follows a family set in the great deppression era, when jobs were very rare to stumble upon and it was very hard living in general. The family goes on a trip to find better jobs and a better life. Throughout the story the family has to deal with a lot of hardships, but what I love is that the ending is very open and sweet. It sort of ends in a positive way, even though the story is very hard and dark.

What I also love is that in between chapters he usually has small off-topic chapters as well, these don't contribute directly to the story line but they add extra flavor to the story.