The first Halo book is "The Fall of Reach" by Eric Nylund, published in 2001. This was followed by "The Flood" in 2003, "First Strike" in 2003, "Ghosts of Onyx" in 2006, "Contact Harvest" in 2007 and "The Cole Protocol" in 2008.
Halo is a series of military science fiction novels written by various authors, including Eric Nylund, William C. Dietz, Joseph Staten and Tobias S. Buckell. It is based on a popular video game. The books are about the war between the human race and an alien race called the Covenant. The main character is a Spartan called Master Chief. Besides the main novels of the Halo series described above, there are also graphic novels, companion books, a short story collection, Forerunner trilogy books and Kilo-Five trilogy books. The details of the chronological order of all these books including their year of publication can be found at OrderOfBooks.com.
The Forerunner series is set 100,000 years before the events of "Halo: The Flood." It consists of "Cryptum," published in 2011, "Primordium," published in 2012, and "Silentium," published in 2013. The Forerunner series is written by Greg Bear. The Kilo-Five trilogy books consist of "Glasslands," published in 2011, "The Thursday War," published in 2012 and "Moral Dictata," published in 2014. The Kilo-Five trilogy is written by Karen Traviss.