While Linux is 'UNIX-like' rather than an actual certified UNIX, any of the UNIX reference books will be close enough for most purposes. A big part of Linux is

While Linux is 'UNIX-like' rather than an actual certified UNIX, any of the UNIX reference books will be close enough for most purposes. A big part of Linux is that a particular distro will come packaged with lots and lots of apps, apart from the underlying operating system. Another main difference between Windows and Linux, is that Linux distros have package managers for 'downloading' apps built-in, so you never need (or extremely rarely) to go wandering around the Web looking for software to download. You merely open up the package manager, search for what you want, click to select the package, then click to install. And that's that. Whenever there's an upgrade, your new package will be automatically upgraded too.