I just thought I'd link to a couple of damn useful and interesting space books you can download. First, one about designing for humans in space:
http://flightprojects.msfc.nasa.gov/book/rp1324.html

Heaps of them here:
http://www.hq.nasa.gov/office/hqlibrary/books/nasadoc.htm

Jim Oberg's site has some interesting stuff. Some PDF books to download if you click on BOOKS in the menu.
http://www.jamesoberg.com/

Connecting Quarks with the Cosmos: Eleven Science Questions for the New Century (http://books.nap.edu/books/0309074061/html/index.html)