The "Intelligent Investor" by Benjamin Graham Revised Edition Updated With New Commentary by Jason Zweig.
"The Little Book on Common Sense Investing - 10th Anniversary Edition" by John C. Bogle.
"Winning the Loser's Game" by Charles D. Ellis.
"Simple Wealth, Inevitable Wealth" by Nick Murray.
Reading these books over-and-over keeps me focused on what is important to my investing success.
Disclosure: I am/we are long VT.