I don't know quite what info you want and I can't tell you much that is not available on the web or in Flayderman's. AFAIK, there is no book devoted to solely to the Starr revolvers, but they are included in several books on CW arms.
The action is interesting. It is often called a "trigger cocker" because with the selector down, pulling the trigger does not fire the gun, it only cocks the hammer. The trigger is then released, and the trigger finger inserted in the gap between the trigger and the rear of the trigger guard, where it can press the sear and fire the gun single action. The so-called "double action", with the selector up, allows the trigger to press the sear and simulate double action firing. The action is the same except the trigger activates the sear rather than the shooter.
The hammer cannot be pulled back for "single action", nor is it meant to be; the small spur is only to allow lowering the hammer without firing.