Please do not read Mantak Chia books on Qigong. He is considered a fraud by many.
Just like authentic Yoga has been corrupted in the West by incompetent teachers and plain charlatans, so is the case with Qigong. You should always go to the original sources i.e. Chinese works where possible. To that end you may find the following helpful;
Some of them may be expensive because they are hard to get but no need to pay too much for any of them. You can get authentic works from the website "china-guide.com".
Just like authentic Yoga has been corrupted in the West by incompetent teachers and plain charlatans, so is the case with Qigong. You should always go to the original sources i.e. Chinese works where possible. To that end you may find the following helpful;
1) Qigong Essentials for Health Promotion - https://www.amazon.com/Qigong-Essentials-Health-Promotion-Gu...
2) Chinese Qigong Therapy - https://www.amazon.com/Chinese-Qigong-Therapy-Zhang-Mingwu/d...
Some of them may be expensive because they are hard to get but no need to pay too much for any of them. You can get authentic works from the website "china-guide.com".