These are two books some westerners are fond of quoting. Sinologists are addicted to these two books as if they were the most authoritative books in ancient China. In a way, it is true. These are very comprehensive books compiled in a very rigorous way. However, they are both of encyclopedic nature.
Huai Nan Zi was compiled by Liu An 劉安, the King of Huai Nan 淮南王 (179-121 BCE). The work was mostly done by his guests and was divided into 21 Inner and 33 Outer Chapters. The Inner Chapters were about the Dao. The Outer Chapters were about other philosophies. What remain today are the 21 Inner Chapters. These chapters are about the Dao of Nature. It is an integration of Daoism 道家, Moism 墨家, Yinyangism 陰陽家, Faism 法家 and Confucianism 儒家 with an inclination towards Daoism.
Bai Hu Tong was compiled during the reign of Han Zhang Di 漢章帝 (58－88 AD). The work started in the year 79 AD when he summoned his officers to hold a conference. The results were recorded and compiled by Ban Gu 班固, a famous scholar. This becomes the standard answers to questions about the study of Jing Xue 經學. It is interesting to find that this book even included a section on sex education.
Anyway, because of the encyclopedic nature of the books, they are not really reliable at the expert level. To call someone a walking encyclopedia is actually calling him someone who knows superficially almost anything you can name but expert in nothing.
I remember I started trading in gum rosin in China in 1982. I looked up the Encyclopedia Brintanica about gum rosin before I went to negotiate a deal. Armed with the detailed information from the authoritative source I was confident that my knowledge was at the expert level. Fortunately I was a good listener and not a big talker. I was surprised that even the categorization of different grades of the product was not the same from the book and as used in the insdustry.
There is always a danger to rely on reputable source of information.