Books that have substantial value were printed prior to which year?

Books that have substantial value were typically printed prior to 1820 due to several factors related to their historical significance, rarity, and the evolution of the printing process. The early printing presses, developed in the 15th century, created a significant shift in information dissemination, leading to the production of many notable texts that are highly regarded today.

Before 1820, you have the works produced during the formative years of print culture, which include many first editions and influential texts in literature, science, and philosophy. The value is also associated with the limited number of copies that were printed, making surviving copies rare and sought after by collectors.

In contrast, books printed after 1820 generally do not carry the same level of historical importance or rarity, as the improvement in printing technology and mass production made books more accessible and widely available. This shift meant that while some books published after 1820 can certainly be valuable, they often don’t have the same level of demand in the rare book market as those printed earlier. Thus, the correct understanding of substantial value in books points towards those printed before 1820.