As of November 2013, 40 Discworld books have been written. Although they can be read independently from each other, a number of novels and stories can be grouped together into grand story arcs dealing with a set number of characters and events, and some books refer to earlier (or later) events.
In this column, the books have been categorized into blocks according to the story arc they can be grouped into, and have been sorted by release date. Some books can belong to multiple arcs, so some overlap between blocks occurs. A suggested reading order, as well as an overview of connections between books and story arcs, can be found at http://www.lspace.org/books/reading-order-guides/the-discworld-reading-order-guide-20.jpg