The Named is by Marianne Curley. The first book in the Guardians of Time series. Ethan is a Guardian of Time, a secret group of gifted warriors whose job is to make sure the forces of chaos don't affect the future by changing the past. When he is given an apprentice to train, he discovers that Isabel may be the key to deciphering a prophecy that will affect all the Guardians.
Ratings: 8th grade - 8 out of 10.