Much of it pretty basic and there are spots that really could have been left out or at least shortened, such as walking through the Tails installer. However, it does get better as it goes and it does a good job of covering a broad range of Linux security topics. Seasoned pros aren't going to take anything from this, and it shouldn't be you first exposure to Linux administration, but I'd recommend reading it to beginner and intermediate admins or "Power Users".