New Blood tells you what happened to Buck between ODST and 5; Hunters in the Dark introduces you to Vale, Escalation to Tanaka and Nightfall to Locke; however none of these appear to actually give you anything more for Halo 5 than the character's backstory.

MacGyver has you covered on Hunt the Truth, but you really should pick up the Escalation comic series as it gives you great insight into the post Halo 4 universe. Specifically issues 8-10 (Chief's next 72 hours after H4), and issues 13-16 and 19-24 (which are direct continuations of the Spartan Ops storyline - which I think is going to be very important in H5....).