I'll let others respond to your book vs. course learning decision.
I will remind you however, that one can learn sailing using Nike's, "just go do it" philosophy. If there is a yacht club nearby, go chat with them about joining a boat for "informal" racing. There are plenty of owners in my club that are more than willing to take on new people as "unskilled laborers". This won't work for more formal races, but it will get you a start and some "networking" leverage. You may not care to race, but that is usually the easiest established method to get you into other on the water opportunities - day-sailing or cruising.
You needn't be a YC member to crew, but check to see if the club has a special membership for crew - ours does for singles, or couples that are not boat owners, but participate as crew. Once part of a YC you will find plenty of opportunities to get on boats and learn the sport. Then you can decide whether or not that ~$700 course certificate is necessary to the type of sailing you want to do.
And Thank You for your Naval service!