2099 UG Continuity Guide and Releasing Order

Marvel 2099 "One Nation Under Doom" saga to the beginnings of the Ghostworks 2099 UG

Doom 2099UG #1-#3 (Happen directly after Doom 2099 #38)
Spider-Man 2099UG #1
Morbius 2099UG #0-#3
Punisher 2099UG #0-#8 (Takes places after the final issue of Punisher 2099 series)
Fantastic Four 2099UG #1-#4 (mini-series, takes place after FF 2099 #4)
Iron Man 2099UG #1-#3 (Volume 1)
Ghost Rider 2099UG #1
X-Men 2099UG "Gravity"-#37 (series takes place after X-men 2099 #31)
Thor 2099UG #1-#2
Hulk 2099UG #0-#3

Beginnings of the Ghostworks 2099 Underground to the "Fall of Alchemax"

Spiderman 2099UG #2-#7
Morbius 2099UG #4-#11
Ghost Rider 2099UG #2-#10
Punisher 2099UG #9-#17
Thor 2099UG #3-#10
Doom 2099UG #4-#15
Salem 2099UG #1-#7
Iron Man 2099UG #1-#4 (Volume 2)
Archangel 2099UG #1-#11
X-Men 2099UG #38-#50
Tensen 2099UG #1-#14
Hulk 2099UG #4-#5
Captain America 2099UG - The Legacy Collection
Black Panther 2099UG #1-#4

"Fall of Alchemax" to the "Coming of Galactus" & 2099 New Year's Eve

Theater of Pain 2099UG #1-#4
Doom 2099UG #16-18
Captain America 2099UG - The Deadpool #1-#4
Spider-Man 2099UG #8-#9
Salem 2099UG #8
Alpha Flight 2099UG #1-#5
The Coming of Galactus 2099UG #1-#4

2099 New Year's Eve and onward...

2099UG: Tomorrow Anew
2099UG Tales #1-#2
X-Men 2099UG #1 (Volume 2) and onward
Iron Man 2099UG #1 (Volume 3) and onward
Null 2099UG
Daredevil 2099UG