So guys, heres some things that you need to know from the first book to understand the second:

like the grouping of Forerunners
 The way Forerunners are grouped places them into four groups: Builders (advancing their technology, and running the Species as a whole), Miners (the ones who gathered all the materials needed by all Forerunners), LifeWorkers (who preserved and studied life, making sure all life in the universe was thriving), and Warrior Servants (when peace was broken by a species, they would put down any threats restoring peace), prioritized in that order (surprising how the LifeWorkers are nearly the lowest?). all held together by the mantle, the way of life built on preserving all life. Forerunners go through natural metamorphosis bringing them into there next step of evolution, the first step being a manipular as a Forerunner would be observed as a child. A manipular had to achieve several goals before entering his first Transformation, several of which were with a Forerunners father or mother (respectively) and Failure to Achieve said goals would be dishonoring ones family, as one did not receive a name until evolution has been met. lastly, all Forerunners had a suit of armor, each equipped with an ancilla, or AI. these suits provided anything needed to survive, within one, you do not grow old, you need not sleep, and you need not eat, all is handled.