'The Nature and Origins of Modern Mathematics: an Elementary Introduction' could be a nice complement to the suggestions already here. It's very much first prin

'The Nature and Origins of Modern Mathematics: an Elementary Introduction' could be a nice complement to the suggestions already here. It's very much first principles, but in a comprehensive and interesting way. You can download it here: http://cupid.economics.uq.edu.au/mclennan/NatureOrigins/natureorigins.html http://cupid.economics.uq.edu.au/mclennan/NatureOrigins/natu...