http://www.history-on-cdrom.com/id88.htm
These are the real manuals in pdf format. I purchased ONI-208J (Revised) from them last year. No worries on the authenticity. Great manual.
Japanese Naval Vessels of World War Two as seen by US Naval Intelligence (ISBN 0-87021-314-8) is reprint of ONI-41-421, Index to all Japanese Naval Vessels, ONI 41-42, Japanese Naval Vessels, ONI-220J Japanese Submarines, and ONI 225J Japanese Landing Operations and Equipment.
The book is out of print but can be found quite easily through online used book search engines. Plus you can save some cash buying the hard copy as opposed to the CDs of these manuals.
Cheers!
