Birdsong by Sebastian Faulks made quite an impact on me. Some parts of the book are incredibly gory and gut wrenching but overall it is such a great story that I had to keep reading on.
The story is set in France before, during and after World War I. It is intensely romantic whilst being very realistic about war itself. There is a bit of sex stuff in the novel.
It is 20 years since Birdsong was first published but don't let that put you off. It is haunting and beautiful and harrowing.