Having obsessed over the pages of As I Lay Dying by William Faulkner as a youngster, seeing that it entered the public domain in the USA as of 1 January 2026 made me feel extremely old.
It's interesting that many see these public domain dates as granting unlimited use to all aspects of well-known works that have fallen out of copyright. However, the territory concerned, other forms of IP such as trade marks, more recent character designs, adaptations enjoying copyright, or the appearance of a particular published edition, should still be considered by third parties seeking to take advantage of works entering the public domain.
My previous comments on some of these issues can be read here: Public Domain doesn't mean free rein - IP Pitfalls for animators and creatives to avoid.
Due to differing copyright laws around the world, there is no one single public domain, but there are three main types of copyright term for historical works which cover most cases.