I'll filter for books that are not only excellent in their own right, but dovetail with some of the best Mustachian insights.
The Economy of Cities by Jane Jacobs. This is a brilliant treatise on human innovation, prosperity, and cooperation. I have never met anyone who wasn't moved by this book. I am convinced Jacobs is one of the most underrated American thinkers of the 20th century. Will change how you view everything from zoning and urban planning, to education and specialization, to the nature of innovation and prosperity, to DIYship versus paying someone else for their expertise.
Zero to One by Peter Thiel. Ostensibly about being a startup founder, really a handbook on how to change the world. Doing things that have never been done, versus replicating established ways of doing. I think the book could be more explicit that some of the most important "startup founders" are doing remarkable, innovative, one-of-a-kind, tremendously valuable work...in their families and communities. It's not captured in GDP and it's not hailed in the newspaper, but the ethos of Zero to One is there for everyone. Start up a book club in your neighborhood. Volunteer for an after-school program or summer sports league. Find your co-conspirators, make deliberate plans, change the world.
When Helping Hurts by Steve Corbett and Brian Fikkert. From a Christian perspective, this book details how wrong we get it when it comes to charity and poverty alleviation. Remarkable combination of quantitative / social science analysis, paired with remarkable anecdotes from their vast experience in the realms of foreign aid, domestic and international nonprofits and charity organizations, and local efforts of churches in the United States to serve in their local community. One of the authors works in the Christian nonprofit realm, the other is a Yale Economics PhD / professor. Impossible not to make the connection between how Mustachian ways of living / doing not only build resilience that allows us to better help those in need, but also models ways of living that allow others to experience the best of life. I care a lot about poverty alleviation (across the social - material - spiritual dimensions of the word) and this book changed the way I view much of it.
The Road to Character by David Brooks. Brooks can be hit or miss (read his NYT columns regardless) but this book is a 99% hit. Learned things about some truly remarkable people. Fundamental takeaway: if developing / strengthening your moral character, virtue, wisdom, and knowledge is not a deliberate effort and priority, you will probably fail in achieving most if not all of the technical, material, or professional goals that you hold dear. Embed yourself in institutions, communities, and processes that will attack your weaknesses and strengthen your character muscles. Commit. We're really good at the competitive / technological / productive development side of our culture, but weak in the dimensions of virtue / commitment / knowledge.