One personal advice: if you want to learn a subject, don't focus on one book, one author or one set of suggestion. Only care about what makes your mind walk the domain.

I spent a decade with a terse text book on abstract algebra and went nowhere. It's for people who are either already enjoying concise math theorems or have the nack for it. I was missing a few bricks. A few years later some guy here or on reddit suggested a book that is vastly simpler, so simple it felt like HS but it cleared a few misunderstandings I had about notation and meaning. All of a sudden that 5$ ebay book had more value that my 100$ old paperbrick.