Regeneration is GREAT. I read it eight years ago and this is what I said at the time:

Regeneration does two things better, I think, than any other book I have ever read: first, convey the sheer horror and senseless damage of World War I; second, convey the kinds of things that the mind can do to itself when dealing with that kind of strain, and convey them with understanding and compassion and respect. Very few books deal with invisible illnesses well. This does.

And eight years later I think that is still true; I cannot think of another book I've read that does it better.