Books evolve and build on each other. All books have mistakes, weaknesses, and strengths.

Franklin Mallory's "The Krag Rifle Story", was the pioneering work. Mallory improved a lot of things with his Second Edition and included Krag SRS data, in the appendix. Karl Egil Hanevik (a great author of Krag books in the Norwegian language) contributed great material on Krag prototypes and U.S. Trials Rifles.

William Brophy's, "The Krag Rifle", nicely complements Mallory's work. The photographs, paper and print were improved. The Norwegian and Danish material was done by Sigurd Halverson and (IMHO) is far better than Olson's coverage in the "KRS".

I like the Poyer & Riesch work, "The American Krag Rifle and Carbine". It is an inexpensive and handy 'field book', with excellent pictures and side-by-side comparisons. (I have a couple copies and take it to gun shows and on trips for a handy reference).

The Poyer book has some minor mistakes, maybe false assumptions on production dates, and breaks things down into "TYPES", that are not official or accepted nomenclature. I find the "Poyer Book" very useful.

FWIW - Joe Farmer (5Mad Farmers) routinely vilified the 'Poyer book' on the KCA Forum and said it was only useful for "lining a bird cage".
(I never really knew what that venom was all about. I also, long ago, ran afoul of Mr. Farmer).

Joe Farmer has a highly regarded, 'self published' work that is advertised in the KCA Classifieds. I have not seen a copy, yet. I accept that it is 'A Must Read' with an entirely different approach, with novel insights, and amazing observations and original pioneering research.

I am lead to believe the published picture quality is poor, but, this is 'corrected' with an allowed access to Joe Farmer's web sight. (Others on this Forum would have fuller insights into this publication and internet access).

(FWIW - "Mallory vs. Poyer" is knd of an ironic Title. Poyer obviously drew heavily on the work of Mallory, Brophy, and many others).