

Both of these books are from the Wayward Children series. The first book was Every Heart a Doorway, which sets up the world: Every now and then a magical door to another world opens. It's almost always for children (because they're less attached to the reality of how our world should be), and almost always it's for a girl (because boys tend to be louder and harder for parents to lose track of). Each book after the first features one character, and all of them happen before book #1.
I was worried the other books wouldn't be interesting, since book 1 would spoil them are, but happily I was wrong.
Also, you can read them out of order, which I did by mistake.
Down Among the Sticks and Bones (Wayward Children Book 2) by Seanan McGuire. This one was about twin sisters with awful parents. The parents wanted them just for a status bump at work and at social events. A door to a world called The Moors opens for them. A world where vampires, werewolves, and monsters under the sea are real. The twins are split up, one living with the vampire lord and the other with a mad scientist. One twin was healed by her new situation and the other was damaged further.
Across the Green Grass Fields (Wayward Children Book 6) by Seanan McGuire. In this book, an intersexed girl had a door open for her to a world called Hooflands. It was populated by all mythical creatures with hooves. She was taken in by a centaur herd, and they quickly became her new family... before she had to leave to save their world.
Both of these books were wonderful! It felt like the author was reading it to me, like her voice was in the room with me. The worlds were so interesting and unique, and I loved all the characters from main to minor.
The one complaint I had about them (about the whole series) is how short each book is. It takes me about six hours to read a YA novel, eight an adult novel, these took about two hours each... I wanted so much more!