I am probably going to review this movie at length in a few days. It is worth to look into some cultural elements.  Here, as a starter, 10 reasons why you should watch Merry Christmas Mr. Lawrence.

1. Highly original. Really not your everyday material.
2. It is not sufficiently known or almost forgotten.
3. POW movie that is by many people believed to be better than Bridge on the River Kwai.
4. The main title, Forbidden colors, is very haunting (there are two versions, the instrumental one by Ryuichi Sakamoto and the vocal one by Sakamoto and David Sylvian).
5. Beautifully filmed.
6. Japanese culture and esthetics (Samurai, hara-kiri, honor, belief in demons and what not).
7. Not your average war movie theme. Captain Yonoi is tragically attracted to Maj Celliers.
8. Nagisha Oshima has directed it (he is famous for his very sensuous and erotic movies, albeit bordering the sadomasochistic. Undertones are clearly present here.)
9. Great acting. Not only by the two singers Ryuichi Sakamoto and David Bowie but also by Tom Conti and Takeshi Kitano.
10. Very impressive. Once you have seen it, you will never forget it.