Final answer:
A book published after the death of its author is known as a posthumous publication. This term specifically denotes works that are released after an author's demise and are often celebrated as part of the author's continued legacy.
Step-by-step explanation:
A book that is published after the death of its author is referred to as a posthumous publication. Unlike a postscript, which is a note added to the end of a letter or book, or a post-publish action, which isn't a standard term in the publishing industry, posthumous specifically denotes works released after an author's death. Such publications can contain a foreword or an afterword by a different writer or editor, who might provide additional context or discuss the significance of the work. For example, if Virginia Woolf had written a book that wasn't published until after her death, that book would be considered a posthumous publication. This sort of release often adds to the value and curiosity around a literary work because it becomes a part of the author's legacy that they did not live to see in print.