I too was disappointed in the Testaments. It was good in parts but the "twist" was predictable and the ending was a bit fairytale.
The original book is flawless. I read it when I was about 16 and it made me a feminist. I'm 50 and the book still gives me goosebumps. And in all those years very little has changed for women - our rights remain fragile, we die in droves from male violence, governments don't listen to us and our physical needs are disregarded.
The other powerful book that added to my feminism was Invisible Women by Caroline Crido Perez. Not a feel-good or fiction read but it does demonstrate that the needs of 51% of the population have been missed out in a society.
I'd give those and the Female Eunuch to every teenage girl to read.
And then I'd sit back and watch the sisters sort some shit out.