If it is a modern publication, there is no unified standard. Generally speaking, it has not been reprinted for many years, and it is difficult to buy out-of-print books on the market. It's best to consult the experts in this industry for the standard of judgment. An easier way is to check whether there is this book on the old books websites such as Confucius Old Books Network. If there is no, or there is, the price is very high, which can basically be called out of print. For example, Reading by Zhai, Secretary of the County Party Committee, and Understanding of Zhi Zhai were out of print two years ago, but they were not out of print after being reprinted by Shanghai Ancient Books Publishing House recently. However, collectors still admire the first edition, and the prices vary greatly.