The financial independence genre is well-populated with books about safe withdrawal rates, index fund allocation, and the mechanics of early retirement. Those books exist, they are useful, and I am not recommending any of them here. The problem they solve is a financial engineering problem, and it has been solved adequately enough that the marginal value of another book in the genre is low. The problem that has not been solved — the one that precedes every investment decision — is the question of what you are trying to become free to do. The books below are the ones that actually address that question.
The most direct treatment is Man's Search for Meaning by Viktor Frankl. Frankl was a psychiatrist who survived four concentration camps and emerged with a theory that applies directly to the financial independence question: meaning is not found in freedom from constraints but in freely chosen commitments to something beyond yourself. The pursuit of financial independence, taken to its logical conclusion, produces freedom from obligation. Frankl's argument is that freedom from obligation is not sufficient for a good life and may be actively harmful to it — that what gives life structure and intensity is not the absence of constraint but the presence of something worth straining against. This does not argue against pursuing financial independence. It argues that pursuing it without having a clear answer to the "what then?" question is optimizing for the wrong variable. The book is short, concentrated, and irreplaceable.
Meditations by Marcus Aurelius is relevant here for the Stoic doctrine of indifference to externals — which is the philosophical framework most aligned with what the financial independence community is actually practicing, whether they know it or not. Aurelius was the most powerful man in the world and spent his private journal arguing that wealth, status, and influence are not goods in themselves but instruments that can be used well or badly. The discipline the Stoics called preferred indifferents — things that are fine to pursue but should not be conditions of your happiness — maps directly onto the attitude toward money that makes FI a useful project rather than a compulsive one. If you are pursuing financial independence because you need to feel safe, Aurelius is worth reading before you hit your number; if you are pursuing it because you have a clear project you want to give more time to, Aurelius will confirm you are doing it right.
The Tao Te Ching in Stephen Mitchell's translation is the most compact account available of the case for sufficiency — the idea that enough is a real category, not just a number on a spreadsheet, and that knowing when you have enough requires a kind of attentiveness that consumer culture actively works against. Mitchell's version is readable in an hour. The argument runs throughout: the Tao gives without accumulating, acts without possessing, leads without dominating. For people who have developed an awareness of their own patterns of grasping and avoidance — which is what financial independence planning often produces as a side effect — the Tao Te Ching provides a philosophical vocabulary for what they have noticed.
John Williams's Stoner is the most uncomfortable book on this list for FI readers, because it depicts a life that is, financially, a near-complete failure — Stoner spends his entire career as a junior professor, never advances, leaves nothing behind in the ordinary sense — and insists that the life was nonetheless worth living. Not comfortable, not successful, not recognized. But worth living. The argument Williams makes is entirely about the quality of engagement with work and with other people, stripped of every external measure. For people who are pursuing FI to escape work they find meaningless, Stoner is a useful question: if you could work on things that engaged you at the level Stoner is engaged by his work, would you still be optimizing for exit? Not a rhetorical question. A genuine one.
Joan Didion's The Year of Magical Thinking belongs here because it is about what happens to your planning frameworks when the person you were planning with disappears. Didion's husband died suddenly over dinner and the book is her account of the year that followed — of how grief disrupts the structures of ordinary time, how the future that was being constructed dissolves, how a person who is extremely competent and self-aware can still be overtaken by the irrational. It is relevant to financial independence because FI is an exercise in long-horizon planning, and long-horizon planning is an exercise in imagining a future with certain people in it. Didion's account of the year after that premise was removed is one of the clearest available. It is not an argument against planning. It is an argument for knowing what the planning is actually for.
The common thread: all of these books force the question of what you are trying to make possible, rather than assuming the answer is obvious. Most financial independence literature is excellent on how; these books are the necessary companion on why. They are worth reading before you start optimizing, not after you reach the number and wonder what the number was for.