The most significant types of aircraft operated by the Imperial Japanese Army and the Navy immediately before and during the Pacific War are described in the two main sections of this book, while a series of appendices provides information on less important Japanese military aircraft, foreign-designed aircraft operated by Japanese forces, aircraft carriers and tenders, aero-engines and aircraft armament.
Comment: There is a commonly seen scan of this excellent book, which is present at many forums etc. and has got size of about 61 MB, but it's incomplete, as it ends with page 509 and lacks several appendices. Luckily, this one file is complete.