Which Sino-Japanese War?

For the Second Sino-Japanese War: Try Shanghai 1937: Stalingrad on the Yangtze by Peter Harmsen for one of the best books I've read on a very specific (and important) battle.

For a broader look at the war, try Forgotten Ally: China's World War II 1937-1945 by Rana Mitter. It's not super academic and I think it focuses on the Chinese point of view a bit too much, but its very readable and is a great introduction to the war.

For the First Sino-Japanese War I'd recommend The Sino-Japanese War of 1894-1895: Perceptions, Power, and Primacy by S.C.M. Paine. It's the best book I've read on the war, which in general suffers from a serious lack of English literature