Read it 3rd and did the tandem read and it was the best experience of my life. Absolutely life changing. I don’t even read it first on my rereads. It ties in better overall to read it after a few books due to specific character appearances you may forget throughout the series. Plus the angst hits harder when you have anticipation building up. You know what’s coming but you don’t know how.
I'm on Heir of Fire rn but I read AB after Crown of Midnight. I think it worked out a lot better for me personally because the majority of the world building is done in Throne of Glass. Also I think I would've been super bored with AB if I read it first and wouldn't have cared about Celaena AT ALL tbh (but I've heard a lot of people say the opposite so idk)