I don't think "Gund Digest Book of SIG-Sauer Pistols" is still in print, but should be available on Amazon or E-bay. Double/single is manageable, but does take more practice and training than a single pull, particularly since there's decocking to think about.
From Swissmen to SEALs, SIGs have a long and noble history as excellent defensive pistols. If you prefer a single trigger pull all the time, options range from the DAK trigger option in the SIG-Sauer Classic line, to the single action SIG 1911s, to the double action only polymer P250.
Best of luck,