Scott Duff's is the second one for when you start needing more detailed information. I normally tell folks that the first to get is Bruce Canfield's on Garands and Carbines - it is a great overview and will let you get a good taste of all the different areas and allows you to find which is the most enticing to you. Then get Scott's red book and you can go happily broke trying to replicate what you find there, like the rest of us ...

AMHO - best regards ...