I agree with Paul regarding the
Miles Vorkosigan series by Lois McMaster Bujold. However, most of the series is
available free from the 5th Imperium on the Cryoburn CD. Cryoburn is the newest book in the series. It wasn't as good as the earlier books.
Although Lisbeth Salander is a genius, I thought the Steig Larsson series featuring her (beginning with
The Girl with the Dragon Tattoo) was very badly written. I know that it is an international bestseller, but bestseller, well-written, and worth reading are not equivalents.
Kenny's suggestion of
Flowers for Algernon by Daniel Keyes is an excellent choice.