"A Confession" by Leo Tolstoy [1]. An autobiographical story of Tolstoy's "search for meaning" when he was, I believe, around the same age. A masterpiece in around 80 pages. From a more practical angle, I wish I had had "Early Retirement Extreme" by Jacob Lund Fisker [2] in my shelf at that age. Don't get fooled by the title, this is by no means a "highway to financial independence" book; rather, it's a really deep book about, well, sensible living strategies, considering the world we're in. The author holds a PhD in theoretical physics, and by living with around $7,000 a year as a scientist and postdoc, he retired in around 5 years in his early 30s. It's a book on thoughtful frugality, if you will. 1: https://en.wikipedia.org/wiki/A_Confession 2: https://en.wikipedia.org/wiki/Jacob_Lund_Fisker
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