This writeup discusses things that may ruin some suprises for you, if you haven't read the book

Aside from Mycroft the AI, libertarian politics and TANSTAAFL this book has something else that makes it a classic. Namely, launching big fucking rocks at Earth from the Moon. I know this sounds like I just picked out the most crass sci-fi plot device in a book that was more about humanity and politics, but look at it from the perspective of the colonists on the Moon. What advantage did the Moon have that the Earth didn't? A shallow gravity well. What did the colonists have in abundance? Big rocks. To me, it was beautiful in its simplicity.