My understanding is that this series was not quite as popular as the Nancy Drew books. There aren't as many of the editions out there in used book land as there are the Nancy and Hardy Boys series, but I think I have a good shot at collection them if I am careful and smart about how much I pay. I know that I will find the best buys (and the best seller) at Jennifer's "Vintage Series Books for Girls . . . and a Few Boys." www.series-books.com
The Secret at Lone Tree Cottage (1934)
In the Shadow of the Tower (1934)
The Mystery of the Locked Room (1938)
The Sierra Gold Mystery (1961).
Tomorrow is payday, and after making sure we have water and electricity for another month, I may just visit Jennifer's shop. This will be fun!