This is about how a writer understands and knows the bitcoin journey process and maybe the book you are looking at still has other connections. But he didn't explain the bitcoin process completely in just one book because the author's habit is usually to make readers come back to wait for the release of the next book and this is just my assumption. But if he says out of thin air that bitcoin has irreversibly regressed or collapsed in 2021, then I conclude he's not one of the authors worthy of being a favorite.
Why do I say that because he is too lazy to look for references regarding sources regarding Bitcoin's journey from when it was created to the process of its journey in the market until now. We know the four-year cycle in bitcoin and but to say that crypto in general has experienced a collapse is also wrong because the industry is basically growing.
In my opinion, the writer was just trying to write a book and didn't study the process properly from the beginning until they wrote the book and the writer missed a lot so that when he wrote the book it was based on what he knew and was not correct with exact certainty.
What you say is very correct, the author's lack of references means they write based on what they see and don't look for various references that make their writing appropriate to what is happening and I really believe in the four year cycle in Bitcoin and we can see in these few months the price of Bitcoin has experienced good improvement.
A good writer will look for a lot of information from all sources to complete what he wants to write. It seems like the author didn't look for more information, so there is still something incomplete in his book. Hopefully, buyers of the book will look for other information through it so they can understand Bitcoin and crypto better.
If the author wants to look for information on the internet, he will find many trusted sources, especially if he wants to look for it in this forum. But it depends on his efforts in searching for the information because he may feel that what he is looking for is enough and immediately make a book. People now rely more on looking for information from the internet because there are more sources and they can get more information. And they can get this information for free by just browsing the internet.
If the book's author could have seen what would happen to Bitcoin, he would have felt that something was missing in his book. He will probably release future books about Bitcoin based on what he finds. But it depends on whether he wants to find out more information or not. Hopefully, other book authors can provide more complete information.