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In theory there's nothing in it that you can't read here or on blogs, but it puts everything in one place and makes a clear explanation, consistent from start to finish. It tells a clear "story" if you like, well supported by evidence and a compelling narrator.
I had been reading this forum every day for at least a year when I read Smarter Investing and yet it was reading the book that made everything fall into place.
I just think you get a "deeper" knowledge from books - people in this forum overlook investing psychology and downside risk, for a start.