Any of Jane Austen's work is likely to appear on the GRE Literature exam. Read the Wikipedia entry for each of the following works at least once and familiarize yourself with the main characters.
1. Sense and Sensibility (1811)
-Elinor & Marianne Dashwood; Lucy Steele; John Willoughby; Colonel Brandon
2. Pride and Prejudice (1813)
-Elizabeth & Jane Bennett, Mr. Fitzwilliam Darcy, Charles Bingham, George Wickham
3. Mansfield Park (1814)
-The Bertrams; Fanny Price; Mrs. Norris
4. Emma (1815)
-Emma Woodhouse, Mr. Knightley, Miss Bates, Frank Churchill, Harriet Smith, Jane Fairfax
5. Northanger Abbey (1817, posthumous)--her first completed novel
-Catherine Morland, Henry Tilney, John Thorpe, Isabella Thorpe; parody of the Gothic novel
6. Persuasion (1817, posthumous)
-Sir Walter, Elizabeth, Anne Elliot, Frederick Wentworth, Kellynch Hall (estate)
For the GRE Literature exam, it's worth reading any Jane Austen novel you haven't yet read, though don't read more than 2. In declining order of importance: Pride and Prejudice
If you're pressed for time, or if you've already read them and want to review, there are also pretty faithful film versions of Pride and Prejudice