Junkers D.1. It seems to be a Karaya publication. Lots of info and drawings of an aircraft which was really more of a test and development aircraft than a fighter. Many variations were tried and tested, some quite attractive. Elliptical wingtips, center underwing radiator, streamlined engine panels, you can see the seeds of Luftwaffe design. I may attempt some mods myself. It's a worthwhile book and the D.1 release is only 4 weeks away.