my suggestion is to just start using it. You will quickly run into things you do not understand and consult the internet. Each step will bring you closer to understanding the system as a whole. No book, no matter how well written, is going to enlighten you better than hands-on experience.
Once you have a particular area you'd like to understand more about (more focused than just 'the system as a whole') you can look for a book that addresses that particular topic.
L7Sqr
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