Reddit mentions of Troubleshooting the Cast

Sure those can help, nothing about casting has changed per se, but there you may find modern instruction to be a lot less rigid. There's been more of an awareness in recent years that there is more than one way to skin a cat.

I used to dabble in competition distance fly casting, for example, and I was told on many occasions that an open stance cast (like Lefty teaches) could never deliver a fly more than one hundred feet. I would just strip off the line, lay the fly down at 105 feet or whatever, and ask them to explain again why it was impossible. They couldn't -- they were all operating on received wisdom.

The machine I described was invented by Bruce Richards, who ran the Scientific Anglers fly line lab for many years, and Dr. Noel Perkins of the University of Michigan. https://en.wikipedia.org/wiki/Fly_Casting_Analyzer

That machine helped show that a good caster makes the fly rod behave in the same way, even if the caster himself may stand a little differently or drop his shoulder a bit more, etc. Humans have different physiques, so biomechanically there is more than one way to make the rod do what we need.

The best casters in the world are all built like fireplugs and tend to cast directly over their shoulders, so they can maximize the strength of their back and chest muscles. That is the traditional method of casting, but personally I question whether the way they do it is required to make those massive casts or if it is just confirmation bias. The only time I ever stood on a podium and made a distance cast in competition with those guys, I think my best shot was 108', and Steve Rajeff (the best caster ever) used the same set up to throw 112' and win the tournament. I am absolutely nowhere near as good a caster as Steve Rajeff, and what that suggests to me is that style doesn't matter; it's just discipline and experience that count. Rajeff happens to be in the over the shoulder school, and is also the best caster in the world, but there's no telling what he might have been if he had decided to cast the way Lefty teaches for his whole career instead.

I'm probably overkilling on the explanation for a guy like you who is just starting out, but the takeaway is that you can learn to cast in several different ways and all will work. I think Lefty's is the fastest pathway to success.

One more excellent book once you get going: "Troubleshooting the Cast" by Ed Jaworowski. I think every angler should own this book and I believe it to be the most effective written tool in existence once you take the first step past 'rank beginner'.

https://www.amazon.com/Troubleshooting-Cast-Ed-Jawrowski/dp/0811729427

Great book full of easy to understand diagrams.

Last thing, here is a piece on ten common mistakes and how to fix them:

http://www.itinerantangler.com/blog/podcasts/2016/01/13/ten-most-common-casting-errors-and-how-to-fix-them/