I read "A City on Mars" last year, and it opened my eyes to just hard space travel is. The government constraints on aerospace projects doesn't help. There's a reason SpaceX moves so much faster; they don't have to justify and explain things to taxpayers.
Beyond that, the book makes a good case for how unrealistic a long-term colony on Mars is... at least in the short term (Short being the next 50 to 100 years).
My biggest take away is: for all his talk, Musk basically just wants to be the Uber to Mars: shuttling people there and back. He don't seem serious about _actually_ solving the problems of how to stay alive and thrive once we get there.
I found it sort of depressing as first, as I'd love to see people loving on Mars in my lifetime. But when I thought about it, I saw that they outlined a bunch of really important problems we should be working on as a society. The sooner we work on those problems, the better.