I don't think we should ask about the new thread-bound books, because if they come out of the bookstore, they will basically be marked. Now it is basically copying technology, and there is less printing. Because the quality of modern photocopying books is higher than that of printed books, in fact, such printed books are limited to craftsmanship and have no collection value.
If it is an ancient book, most of the auctioned ancient books and versions have been auctioned.
If the books obtained from private transactions are authentic, it is not just a matter of printed copies and photocopies. There are too many versions of ancient books, which are not photocopies in the modern sense, but "shadow editions", with a large number of printed editions, mostly woodcut editions. There is also the color printing overprint technology developed later.
The main forgery methods include adding celebrity appreciation, cutting and trimming the residual edition as a "rare edition", removing the preface and postscript of the later edition as an early edition or a "rare edition" and so on.
If individuals need to identify books, it is best to consult professional institutions; If you want to learn identification, you only need to read more and check more, supplement all kinds of knowledge reserves such as history and literature, and also need to dabble in the restoration technology of ancient books. There is no end to learning, not a matter of time.
Value judgment mainly depends on authenticity, age, technology, survival number, etc. It also involves the influence of celebrities and changes in market trends.