The fall of Reach came before Halo ce and showed info of the backstory of the UNSC like their history. According to 343 industries the owners of the Halo canon,the books are canon too just below the game canon. They could have kept the canon intact except making the battle several hours longer.The battle was massive and bloody in the books,we didn't saw much of this in the game that's why many of us are disspointed. I doubt that Bungie created the spartan III,i mean they only created the master chiefnthe other spartans were created by others except Noble team. Bungie even uses alot of cool things from the books in their game(like the sIII,commonwealth,orbital defense platforms,...) but yet they ignore and ruin the canon,i think that's disrespectuful to the Halo Story I think you should buy the books,they are a good read :)