Note that the price of the book has got nothing whatever to do with it. You are probably referring to my first book recommendation which some enterprising soul is trying to sell for a huge markup (i.e. $300 because it is not easily available) but i just provided the link for reference. You can get it cheap if you search. Or you can read other cheaper equivalent books, one of which i had also provided as my second recommendation.
Now you asked me to define "authentic" sources in your other post. For TCM/Qigong you would start with publications from mainland China preferably by doctors/professors from a Medical College/University/Hospital who study both modern and TCM medicine. You would then try to get at the root texts for the subject. With these sources in hand, you can now start your study. So here goes;
1) The root text for TCM is "Huangdi Neijing" aka "The Yellow Emperor's Canon of Medicine". Start here: https://www.amazon.com/Illustration-channels-points-acupunct... Also check the website "www.china-guide.com" for authentic books on TCM/Qigong.
Finally here is a paper named "The Man who Invented Qigong" which explains the origin of the word and its current methodology - https://www.qigonginstitute.org/docs/The%20Man%20Who%20Inven...