Out of Perfection by Miranda Dietz

The City of Perfection had remained hidden for over 300 years, encased in a glass pyramid with walls too thick to see through. Many had encountered the pyramid, deep within the forest, but ignored its presence. It appeared to be nothing more than a dilapidated remnant of the old world. No one could have guessed that it housed an entire city of women, each identical to one another. Claire is just one of hundreds of clones in Perfection who believe that the world had been destroyed by a nuclear war. Certain death awaits any woman who goes outside. She detests her job and lack of individuality, but finds solace in forbidden books until her best friend threatens to turn her in. Claire is distraught, but when she finds a tunnel leading out of the pyramid she sees a way to end her suffering. She leaves her home behind, expecting instant death, but instead finds herself surrounded by life.