Via the US PlayStation Blog, the list of PlayStation Now additions for this month is as follows: https://blog.us.playstation.com/2019/05/07/batman-arkham-knight-and-more-come-to-ps-now-in-may/
Unfortunately I don't have access to the European list right now (there's usually a difference between the 2 regions) because I can't get the European Blog to load.
- 8-Bit Armies (PS4)
- Batman: Arkham Knight (PS4)
- Brawlout (PS4)
- Dangerous Golf (PS4)
- Lego Ninjago Movie Video Game (PS4)
- Majin and the Forsaken Kingdom (PS3)
- Metal Gear Rising Revengeance Ultimate Edition (PS3)
- Miko Gakkout Monogatari: Kaede Episode (PS4)
- Sherlock Holmes: The Devil's Daughter (PS4)
- Tales of Zestiria (PS4 Upgrade)
Unfortunately I don't have access to the European list right now (there's usually a difference between the 2 regions) because I can't get the European Blog to load.