Kevin Burton Smith has an excellent summary of the Oliver Quade series over at the excellent Thrilling Detective website.
I have the earlier collection Brass Knuckles, and when this released, I bought it in ebook format immediately to read the four stories that were not collected in that book. The stories are light, fun reads. If you read one or two at a time, they’re good. Otherwise you might overdose on Gruber’s pulp formula.
Links to the books in Ebook and paperback formats: