Ienaga Saburo, The Pacific War is a good way to start the second sino Japanese war readings:

Pacific War, 1931-1945 (Pantheon Asia Library) https://www.amazon.com/dp/B003PJ7G28/ref=cm_sw_r_cp_api_i_Arh0CbTS70ZN9

From a Chinese perspective, good introductions to the period would be Rana Mitter's Forgotten Ally (also known as China's WW2) or Hans van de Ven's China at War. My own preference is for the latter as it covers the prewar and civil war periods as well as the Second Sino-Japanese War, but Mitter's book is much more detailed on the Second Sino-Japanese War in particular. Van de Ven's book is somewhat of a veiled critique of Mitter's in that van de Ven is really keen on emphasising comprehensive military analysis in close conjunction with politics, in contrast to Mitter's more politically-heavy but militarily light narrative.

For something a little more academic, van de Ven's War and Nationalism in China and the edited volume The Battle for China may be of greater interest.

Also, Stephen R. Platt is working on a book on Sino-American cooperation in WW2, but he seems to have only begun researching so it'll probably be a couple of years yet. But watch this space.