I haven’t read Contact Harvest or played Halo Wars. Are their stories alike? If not, which one comes first?
No they are not and Contact Harvest comes first. Only the first three levels of Halo Wars take place on Harvest and that’s five years after Contact Harvest.
No. Well kinda. You’re on Harvest for like 2-3 missions and this is 5-6 years after first contact on Harvest.
As the others mentioned above, no they are not alike. However, I would call them companions in a way, illustrating the early years of the war. In Contact Harvest, the Covenant is encountered for the first time first by the Kig-Yar then a follow-up force of Brutes, completely overwhelming the planet. In addition to Sgt Johnson, Private Jenkins backstory is established here, the green UNSC militia plays the main role in the planet’s frantic evacuation. Side note, the rise of Tartarus and the the Prophets of Truth and Regret occur in the book. Flash forward to Halo Wars, the UNSC finally concedes Harvest, but what the game does well is establish the overwhelming might of the Covenant. Harvest wasn’t completely glassed at this point in lieu of a large artifact found in its polar region (correct me if I am wrong on any points, no worries).
A long story short, no they aren’t the same, but they are connected.