Download instantly and read the entire DDDB offline at leisure on any computer device. That means you can still read it when you are sea, far from any internet connection.
This is the pdf version. It will work on just about any ebook reader or computer, but is perhaps not the easiest format to read. It is, however, the best format if you want to print out sections of it as a hard copy.
If you have an ebook reader one of the other formats is probably preferable. Or you can download a free program such as Cool Reader, which will allow you to read the epub version on your Windows, Android, or Linux tablet or computer.