OK, here we go...
I just finished John Green's newest book, Turtles all the Way Down, and man, that book was something. I personally enjoy John Green's writing style, though I'm conflicted on the subject of his portrayal of female characters. This book, however, was very existential, and very meta, and I related to it on a lot of levels. It's not my favorite book by him (An Abundance of Katherines still holds that title), but reading it felt like a glimpse into the brain of someone who feels my pain.
I have anxiety (multiple types of it). But I don't have it in the same way Aza has it. I don't fear death, and germs don't scare me. I believe that sickness and pain are a part of life, and that it's what teaches us lessons and makes us stronger. I do, however know what it's like to be trapped inside my own brain. I worry about a lot of things, especially the nothingness of life. I worry that my personality is just comprised of my thoughts and feelings, and that there isn't one, specific thing that is the me inside of me (I'm sure you didn't get that reference). Since I was very little, I've wondered about the existential things. I used to ask my parents about things like "why am I the way I am? Why do I think things differently than other people? Why do I know right form wrong? I worried about all aspects of life, specifically consciousness, and the WHY of it. Why do I have the ability to think? Is the way I see the color red the same as everyone else? Everything is relative. My red could be someone else's blue, and we'd never be able to tell because the only thing we can do is compare it to the world around us, which is full of the blue-red, and no one will be able to tell the difference. Why do I care what everyone else thinks of me? And I know that a lot of the answers to my questions can be found in psychology, but the relativity of it still applies. Everyone who studies it says in theory that we should all see things the same, but who really knows if my red is the same as your red? Whatever, I'll sort it out in my own head in due time (which probably means lots of posts about anxiety).
That in no way means that I know how anyone else with anxiety feels, because everyone is different, but from my pint of view, the themes in this book are some that I really relate to, in a different way than the main character.