I also add my vote to the book 'Digital Lighting and Rendering'. Very good, informative book. I still use it for reference.

Regarding the Light Master course. I personally found it useful (but I also got it for about 20 bucks). If I had paid the original full price I would have been very upset.

If the 23.50 offer includes access to the Dreamlight club, then you might want to take advantage of it. There is a lot of information there that goes beyond lighting. There are videos covering postwork, modeling and animation. After I downloaded the Light Master videos I immediately ran over to the Dreamlight Club and grabbed all the videos and ebooks I could lay my virtual hands on.

Just my two cents.