James Clavell's Shogun is a good one to start with. It has it all... samurai, swordfights, ninja, and this one clueless Englishman in the middle of it all... An excellent book. And a thick one, too.
Then there's Eiji Yoshikawa's Musashi. It's a historical story of one of the best swordsmen to have ever lived yada yada yada. I never read it because the book is too damn big. It's enormous. It's the size of those large, ancient Bibles you see in museums. So, if you want to give yourself a hernia, I can recommend this one. Apparently, it's regarded as something of a classic, too, so it can't be all bad...