Ebook
What is an ebook?
An ebook is a book composed or converted into digital format for reading on a computer screen or handheld device.
The question is: if an ebook is simply a book in digital format, that technically qualifies many things that are not really ebooks. It also does not fully define what makes an ebook an ebook. So what does?
An ebook is a non-editable book that has been converted into a digital format to be read on any digital device, such as computer screens or mobile devices.
To understand ebooks better, let us look at their key characteristics.
Characteristics of an ebook
Ebooks are files that can be read on a digital device — a tablet, smartphone, computer and so on. But given that other files can also be read on digital devices (Word documents, for instance), ebooks have specific characteristics that set them apart.
Ebooks must not be editable
A defining characteristic of an ebook: the text must not be editable. An ebook should always be converted into a format that guarantees it cannot be edited. Since thousands of people have access to it through digital devices, they could modify any content without the author's permission. For something to be considered a true ebook, the text must not be modifiable in any way — just like a paperback book.
Ebooks are responsive
Another important characteristic is that true ebooks must be responsive. This means that whatever screen size the ebook is viewed on, it will always adapt to it — the text will maintain its formatting with line breaks, and chapters and images will resize to fit the proportions of the device.
There is one exception: PDFs. Since PDFs cannot be edited but are not resizable, they are technically not considered ebooks under the characteristics that distinguish them. However, because companies take advantage of the ease of downloading and distributing PDFs, they have become "unofficial" ebooks and remain one of the most widely used ebook formats.
Ebook formats
If you searched for ebook formats, you would find quite a few options — dozens, in fact. However, the likelihood of actually using many of these formats is fairly slim. To keep things simple, we will look at just the three best known for their ease of use and their ability to be widely distributed, including for use in web design: EPUB, AZW and PDF.
EPUB (.epub)
An EPUB, or electronic publication, is the most widely supported format and can be read on a variety of devices, including computers, smartphones, tablets and most eReaders (except Kindles). EPUB files are reflowable, making them true ebooks and easier to read on small devices.
AZW (.azw)
AZW files were developed by Amazon for its Kindle e-readers. These files can store complex content such as bookmarks, annotations and highlights. However, AZW files are limited to Kindles or devices with Kindle apps, and can only be accessed through Amazon's online store.
PDF (.pdf)
A PDF, also known as Portable Document Format, is not technically a true ebook by our definition, but it is the format most people are familiar with. Created by Adobe, PDFs are known for their ease of use and ability to maintain custom layouts. Since they hold their formatting and are not reflowable, they can be difficult to read on a small screen. Despite this, they remain one of the most widely used ebook formats, especially among marketing professionals.