<p>The  <em>Adaptation Guide</em> is a practical reference about how to customize — or adapt — an open textbook so that it better fits your needs in the classroom and elsewhere. This guide defines the term adaptation and discusses reasons for revising a book, why this is possible with an open textbook, and the challenges involved.</p> The Adaptation Guide is a practical reference about how to customize — or adapt — an open textbook so that it better fits your needs in the classroom and elsewhere. This guide defines the term adaptation and discusses reasons for revising a book, why this is possible with an open textbook, and the challenges involved.