An electronic book is a digital publication of book-length. It consists of text, images, or both, and is readable on computers and other electronic devices. There are special data-formats like epub, but mostly e-books are in pdf-format. Some publishers publish their e-books with a rights management system (DRM), which allows reading anytime online. To download and save the e-book, you need to install “Adobe Digital Editions” on your computer or tablet and the “Adobe Digital Editions” app on your smartphone. This copy protection software ensures that e-books cannot be handed on illicitly to third parties and are only accessible on your device for the period of “loan”. E-books can be published as the electronic version of a printed book or “born digital” without a printed equivalent. E-books have an ISBN, the e-ISBN.