Right now marvel is offering 12 free trades on their app. The choices you can choose seems to be however many you want. The choices you can pick are. I had a few of these purchased already so i redeemed
Civil war, black panther, thanos wins, dark Phoenix saga, kree/skrull war, black widow, and captain marvel.

The app does not say how long these will be free. I did have to log into the store in chrome to redeem a title the past few days but it may have been my phone causing issues.

Avengers vs xmen
Civil war
Amazing spiderman red goblin (asm 794-801)
Black panther by ta-neshi coates
Thanos wins by donny cates
Xmen dark Phoenix saga (uncanny xmen 129-137)
Avengers kree skrull war
Avengers v1 (2018 #1-6)
Fantastic four (2018 #1-4)
Black widow (2016 #1-6)
Captain marvel (2014 #1-6)
Captain america ed brubaker omnibus(2004 #1-14)