|There is more information available on this subject at Del Rey Books on the English Wikipedia.|
Del Rey Books is a branch of Ballantine Books, which is owned by Random House. It is a separate imprint established in 1977 under the editorship of author Lester del Rey and his wife Judy-Lynn del Rey. It specializes mainly in Science Fiction and Fantasy books.
It has been responsible for the publishing of Halo: The Fall of Reach and Halo: First Strike by Eric Nylund, and Halo: The Flood by William C. Dietz. Del Rey Books will not be in charge of future Halo books. That job will go to publisher Tor.