I'm going to go a bit off the reservation here and recommend Thou Shalt Prosper. It explains why Jews have been more prosperous as a group throughout history, and is written by a Rabbi (so obviously no anti-semitism). Essentially the message is very pro-work and pro-business, explaining why work and business are inherently good activities, that benefit not only you but everyone around you. The mentality of this book is certainly more along the lines of saying that working your whole life is better than retiring early. Not exactly the MMM philosophy, right? So I'll recommend it under four contexts:
1. It has recommendations that will help you prosper during your accumulation phase--having the right attitude to succeed, and reach FIRE more quickly.
2. It also may help you better understand the moral argument behind work and business being good and ethical things--aiding your attitude about work while you are still working.
3. Most people after reaching FIRE, I would argue still are very productive and contributing members of society, MMM included. This material could help you sort out the right attitude of what to do after retirement to stay engaged and happy, rather than feeling lost and isolated, after retirement.
4. Even if you disagree with the work-is-good mentality, understanding your enemy is a good thing, in my opinion!
By the way, it isn't heavy handed religious God Commands You To Do This stuff either--it is written from a very practical perspective. Sure there is scripture quoted here and there, but it's in a very practical sense, explaining how Jewish beliefs and teachings have led to their economic success. Following the book does not require or assume any sort of religious belief.
By the way, along the lines of #4 above, I'm currently reading Against Thrift: Why Consumer Culture is Good for the Economy, the Environment, and Your Soul. I just started it so can't really say whether I recommend it, but I just couldn't pass it up when I saw it on display at the library.