I agree with others on the "Meditations" by Marcus Aurelius.
Off the top of my head, I would add:
* "The Way to Wealth," by Benjamin Franklin: https://www.amazon.com/dp/0918222885 (also available online for free; it's in the public domain) -- no-nonsense practical advice from a super-successful individual
* "The Intelligent Investor," by Benjamin Graham (specifically the chapters titled "The Investor and Market Fluctuations" and "Margin of Safety"): https://www.amazon.com/dp/0060555661
Off the top of my head, I would add:
* "The Way to Wealth," by Benjamin Franklin: https://www.amazon.com/dp/0918222885 (also available online for free; it's in the public domain) -- no-nonsense practical advice from a super-successful individual
* Warren Buffett's Letters to Berkshire Hathaway shareholders: http://www.berkshirehathaway.com/letters/letters.html (also available organized by topic, in a bound book: https://www.amazon.com/dp/1611637589 which some will find much easier to read)
* "The Intelligent Investor," by Benjamin Graham (specifically the chapters titled "The Investor and Market Fluctuations" and "Margin of Safety"): https://www.amazon.com/dp/0060555661
* "Influence: the Psychology of Persuasion," by Robert Cialdini: http://www.amazon.com/exec/obidos/ASIN/0688128165
Also:
* "Devil Take the Hindmost," by Edward Chancellor: https://www.amazon.com/dp/0452281806
* "A Short History of Financial Euphoria," by John Kenneth Galbraith: https://www.amazon.com/dp/0140238565
* "Extraordinary Popular Delusions and the Madness of Crowds," by Charles Mackay: http://www.amazon.com/exec/obidos/ASIN/1586635581