memoir is a document class designed especially for book-length documents. It incorporates the functionality of many independent packages into the class so that instead of loading a lot of packages, you can just load memoir.
Quoting from the manual:
The built-in package functions are mainly related to document design and layout;
memoirdoes not touch upon areas like those that are covered by the
hyperrefpackages or any related to typesetting mathematics.
The Memoir Class 8th Ed. 2010, p. XXV.
[T]he emulated packages are:
verse. As well as the emulated packages
memoirprovides functions equivalent to those in the following packages, although the class does not prevent you from using them:
The class is extensively documented, and even if you don't use it, the manual is a wealth of general information about book design and the standard LaTeX methods for all parts of a document.