Unfortunately, I know of no book that treats Nikon RF lenses the way that Erwin's books and articles treat their Leica analogues. I am a great fan of Robert Rotoloni's and a member of NHS, but his books on collecting or the historical record of Nikons only touch tangentially on the design and performance aspects of the optics; the latter is not their raison d'etre.
I myself have published two articles in the LHSA's Viewfinder journal comparing Nikkor and Leica lenses, one on the 50/1.4 Millennium versus the new 50 Summilux, and one comparing the Nikkor 35/1.8 with the contemporaneous Leitz 35/2 (1st version) and the Canon 35/2. Comparisons in both cases were done with images, but I lack the knowledge of optics to delve further into things the way Erwin does.
There are occasional articles here and there which are satisfying; I recall one on the official Nikon site about the 35/1.8 design, but nowhere is there a comprehensive optical treatise.
