Halo's forerunner trilogy (Part 1 will release this year) book.
Halo contact Harvest
Hao The Cole protocol
Comic Halo Genesis
Comic Halo bloodline
Halo Reach
Halo wars (not sure it was before reach).
Halo 1
Halo the flood
Halo first strike( a part that happens before reach and a part that happens after the Flood)
Halo2
Halo ODST
Halo Ghosts of Onyx
(Comic)Halo uprising (can also read before the Ghosts of Onyx)
Halo: Evolutions (all little stories and many don't really have a time line...some you know that happened after Halo 1 like 'The mona Lisa story)
Comic Halo helljumper (does not really have a timeline but you know if happend for sure after Harvest)
halo 3
But please try to read them for the fun...Because if you are going to be sucked in its history you will see that some stuff in its timeline does not make sense...
