I usually use that youtube to mp3 site to download YT videos, but I don't really like the bitrate of the downloaded video, it's not the best quality. But still, you gotta download what you can before it's too late.
Also, more in terms of a "library" for your personal computer, Calibre is a fantastic management application that lets you read e-books that you might get from Kindle (usually these are .epub files on your device, or .pdf files), on your computer. There's thousands of computer software and programming epub files of textbooks on IT Ebooks; any book published by O'Reilly, usually these books have drawings of animals on the covers, are definitely books you should have in your library.
This is what Calibre would look like on Linux (apologies for the resolution):
Also, more in terms of a "library" for your personal computer, Calibre is a fantastic management application that lets you read e-books that you might get from Kindle (usually these are .epub files on your device, or .pdf files), on your computer. There's thousands of computer software and programming epub files of textbooks on IT Ebooks; any book published by O'Reilly, usually these books have drawings of animals on the covers, are definitely books you should have in your library.
This is what Calibre would look like on Linux (apologies for the resolution):