The Mountain stories are a loosely connected series, and while they are slightly richer if read in order, they are meant to stand alone. All of these men are friends (eventually) and they wander in and out of each others’ stories.
The Kurt and Jake stories
Into the Mountains — prequel — Jake and Kurt have their own reasons for leaving civilization behind
Fire On the Mountain (novel) — they meet
Snow on the Mountain (novel) — their story continues into winter and they meet Mark
Mistletoe on the Mountain (short) — their first Christmas
Blood on the Mountain (novel) — their second ranger season
Coming out from the Mountains — Jake takes Kurt home to the family
The Mark and Allan stories
Fall Down the Mountain (novel) — Mark and Allan meet — approximately a month after Snow
Cross the Mountain (short) — Mark takes Allan skiing
Storm on the Mountain (short) — their first Valentine’s day
Gary and Seth
Return to the Mountain (novel) — Gary and Seth know Mark and Allan from Wapiti Creek and encounter Ricky from The Rare Event.