The two best books to read on the IJN are Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy, 1887-1941 by Mark Peattie and David Evans and Sunburst: The Rise of Japanese Naval Air Power, 1909-1941 by Peattie. These two books are foundational texts on the IJN's origin and how it functioned. Two older books are good for covering the wartime activities of the IJN. Paul Dull's A Battle History of the Imperial Japanese Navy is a good secondary source on the IJN's war. A good compliment to Hara's Destroyer Captain is the second edition of The Japanese Navy in World War II: In the Words of Former Japanese Naval Officers which has a number of reminiscences of IJN officers.

If you're interested in the Meiji/Taisho view of the IJN, J. Charles Schencking's Making Waves: Politics, Propaganda, and the Emergence of the Imperial Japanese Navy, 1868-1922 fleshes out a number of areas in this period Kaigun briefly covers. The two standard reference books for the IJN are Warships of the Imperial Japanese Navy, 1869-1945 by Hansgeorg Jentschura and Dieter Jung and The Imperial Japanese Navy by Anthony J. Watts and Brian G. Gordon, but both are expensive and out of print. Those two reference books are a bit dry, and could be supplemented with Fleets Of World War II by Richard Worth which has some good commentary on the various designs produced around the world. Worth is not always correct in his judgements, but it is an entertaining reference work. The design compromises and consequences of the interwar naval treaties reverberated well into the Second World War and John Jordan's Warships After Washington covers all five major navies' attempts to deal with the system such as the IJN and the French creating beefed up destroyers. Another good comparative read from a technical point of view is Naval Anti-Aircraft Guns and Gunnery by Norman Friedman. Finally, warships are crewed by men, and Ronald Spector's At War At Sea is a social history of naval combat from Tsushima through to the Falklands and covers a large number of navies.