I would recommend Pawn of Prophecy by David Eddings, its a simple story a short book and its part of a big series. You can buy the first 3 in one book 2nd hand from amazon for 4.50usd.
Its more of a young adult book so it should be easy for them to follow.
I would also recommend anything by Terry Pratchett, for great examples of satire anything in the diskworld collection, especially the earlier works, they are shorter.
the original Dragonlance story is also a good read for examples of DnD style stories.
The Innocent Mage (Kingmaker, Kingbreaker) is a great story by an aussie :)
anyway hope this helps