Herb, this has been discussed before (not complaining, I just type like sh$%). I like the Luger Story as a good read, lots of good info, buy it and then those below. The following i like in order of like
Weimar Lugers by Jan Still (its what i collect)
Imperial Lugers JS
Third Reich Lugers JS
Lugers at Random, it is actually all encompassing, and very good, but I like JS's better.
The smaller, cheaper books, don't waste your money or count on them, unless you want to supplement your other luger books.
Ed