How to initially preserve the copyright for a book published in the public domain?

Question

Copyright

In general, there is a certain site of mine, available to everyone.
And on the site, it is planned to gradually lay out the book, roughly speaking, today 1 page, tomorrow another 1 page, and so on.
The book was written by me.
The question is - how can I retain the rights to this book if someone cunningly ### decides to sell it without my knowledge or otherwise receive income from these texts or simply declare that he is supposedly the author? Do I have the right to somehow influence for such actions? And what to do in such cases?
The published texts are also unique content, which is the reason :) for posting it (in this case, I get a profit in the form of unique content for the site and the text is suitable for the subject of the site, which will positively affect the site itself).

Answer 1

From the old common one: print a copy and send it to yourself with a notification and an inventory. Receive the envelope and do not open it until the kurtosis.
Of the more reliable - to endorse the work of a notary.
That is, the proof of authorship will be the chronology - if the notarization or the date of sending the letter to oneself is earlier than the publication by "pirates" - then the court recognizes the author of the first