While I don't personally think that this manga is quite a masterpiece, I do think that it's an incredible story that tackles the topic of mortality in such an honest, varied way that I don't think any other series has ever come close to. I got through the whole manga in one day and I can confidently say that it's motivated me to look at life in a new way so I think it's a definite must-read.
It's also depressing as hell, goddamn