Wikibooks Stacks is the book sorting mechanism for Wikibooks. Here is a hierarchical arrangement of all the books on English Wikibooks (currently 3381 of them), managed by Wikibookian curators with some semi-automated help.

Library stacks.

At the top level, our stacks are arranged into departments — humanities, social sciences, mathematics, and so on. All the sectional units of the hierarchy below that level are called shelves, on which the books are found. Most departments have a top-level shelf shown for general references, and other top-level shelves which are more specific. Shelves may also contain subsection shelves, for the further sorting of shelves.

It takes its name from the stacks of a library, which are the book storage areas, with row upon row of bookshelves tightly packed together.

Information pages

Browse Wikibooks Stacks
At the top of the hierarchy is our floor plan (so to speak) showing all the departments.
Detailed structure of Wikibooks Stacks
A description of the detailed structure of Wikibooks Stacks can be found here.
Curate Wikibooks Stacks
For the most part, the pages in these stacks should detect when they need some sort of maintenance by a human contributor, and provide tools to assist in the tasks likely to be relevant.
Adding books to Wikibooks Stacks
Book can be easily added to Wikibooks Stacks using these directions.
Read about the history of Wikibooks Stacks
This is the most recent form of a Wikibooks cataloging tradition that has been through several incarnations stretching back to the earliest years of the project.