For Free League Publishing's RPG there are two bundles, Mutant Year Zero ($22) and Mutant Year Zero 2 ($20) where the second bundle doesn't have a second tier.

Mutant Year Zero

Mutant: Year Zero (269 pp, 2014)
Zone Sector 1: The Doom Sphere (7 pp, 2015) - scenario location
Zone Sector 2: Denizens of the Sink Hole (10 pp, 2015) - scenario location
Mutant: Year Zero Gamemaster Screen (8 pp, 2016)

Genlab Alpha (240 pp, 2016) - mutant animals splatbook + campaign
Zone Compendium 1: Lair of the Saurians (32 pp, 2015) - three scenario locations
Zone Compendium 2: Dead Blue Sea (44 pp, 2015) - sea-going expansion with two scenario locations
Zone Compendium 3: Die, Meat Eaters, Die! (36 pp, 2016) - five mutant animal smaller scenario locations

Based on Twilight 2K RPG, scenario locations are less than 10 pages containing a map, NPC descriptions and motivations, a couple of plots and a timeline. Kind of a sandbox one-session adventure.

Mutant Year Zero 2

Mechatron (240 pp, 2018) - creating robot PCs + campaign
Elysium (272 pp, 2019) - an enclave (underground pre-fall city a la Paranoia or Fallout) + campaign
Compendium 4: Eternal War (33 pp, 2018) - three robot scenario locations
Compendium 5: Hotel Imperator (36 pp, 2018) - four scenario locations
The Gray Death (104 pp, 2019) - a campaign that ties in Year Zero, Genlab Alpha, Mechatron, Elyium

I think this is most everything that came out for Mutant Year Zero except for card decks, maps and dice, though possibly decks and maps are included but not mentioned (addendum after buying: maps I think included, not decks). I like the idea of a campaign to tie in the four main books so I think I'll buy these bundles.