Personally, I'm a big fan of Heinlein and would like to recommend the following of his works:
Starship Troopers (my favourite book) The Moon is a Harsh Mistress The Door into Summer Space Family Stone (yes it is dead cheesy, but we all have our guilty pleasures) No one seems to have mentioned Kim Stanley Robinson's Mars series, the main three being Red Mar, Blue Mars and Green Mars. He's also done a few short stories based on the same universe which are well worth a read if you like the main three books. Cheers, -- Matthew R Moore Personal - tba LARP - www.pathfinderlarp.org.uk
