The length of a book varies according to the topic and its purpose. Generally speaking, the shortest type of book is typically a short story or novella. A short story is a piece of fiction prose that ranges from 500 to 20,000 words in length and typically has a single plot with a few characters. A novella is a longer work of fiction prose, generally between 17,500 and 40,000 words in length and has more complex characters and storyline than a short story.
While short stories and novellas are the shortest type of books, there are other types of books that can be quite short as well. A pamphlet, for instance, is typically around 1000 to 2000 words long and is usually meant to provide information to readers on a specific topic. Similarly, a brochure is roughly 3000 to 4000 words in length, and is designed to advertise a product or service.
In recent years, the emergence of digital and ebooks has made it easier than ever to access all types of books, regardless of their length. So, while short stories and novellas are generally considered the shortest books, there are plenty of other books that vary in length. Ultimately, the length of a book is dependent on the content and its purpose.
To explore the different types of books and their lengths further, check out this helpful article: https://www.birminghampubliclibrary.org/writers/length-of-books/