Every Day is about a person named A. Because A is without a body, he doesn't have the normal attributes we cluster around identity--gender, race, culture, religion, family, even language change for A every day. (I'm going to refer to A as a he, just so I don't go crazy writing he/she). A wakes up in a new body each day, lives the life of that person with the aid of memories that he can access, and then moves on to another body in a totally unconscious process that takes place each night while he sleeps. It's been that way for A since infancy, and while A doesn't really understand why he's different, he's never told anyone. There are a few parameters: A ages normally (A is now 16, and so only wakes up in bodies that are also 16) and doesn't range too much geographically. A can't choose whose body he will occupy, and is never in the same body twice.
As you can imagine, A is the ultimate loner. With no relationships to anchor him emotionally, A goes through life mostly as an observer--the main goal being not to disrupt or interfere in the lives of his hosts, whatever they are like. But one day A wakes up in the body of a not-very-emotionally-sophisticated 16 year old named Justin and meets Justin's girlfriend Rhiannon. Just like that, A falls in love.
From there, the story launches into a unique courtship. After an idyllic day at the beach, A begins to anonymously seek Rhiannon out, to meet her anew and befriend her each day. He can't bear to be without her. A finally tells her what his life is like, and despite some initial skepticism (of course) she finally believes him. They slowly grow more attached. They sometimes communicate by e-mail, and sometimes in person, but A's changing bodies become an issue. You can see Rhiannon respond differently to him when A occupies the body of a handsome jock, or a really fat kid, or a severely depressed goth girl, or a transsexual. Whether Rhiannon will hold his hand or not depends a lot on what body that hand is attached to. It also bothers Rhiannon that there is a sense that she can't rely on A. He doesn't know what his circumstances will be from day to day. As she points out to him at one point, he's always going to leave her, even if he always comes back.
There are so many interesting and unexpected things about this story and how the relationship plays out, and I thought the premise was really clever. But something bothered me all the way through. The way A experienced infancy and childhood, with a different family each day, should have left him not as emotionally functional and mature as Levithan makes him. Young children do not thrive emotionally with no attachments. Yes, there is an undertone of melancholy and poignancy around A when he thinks of his childhood, but A is not presented as a sociopath (unlike the one other transient soul he meets toward the end). A is a kind, moral, caring person who would probably have no trouble finding love in normal circumstances. I can understand why Levithan set things up the way he did in terms of the storyline, but psychologically it didn't feel right to me. Still, if you can overlook this, Every Day is an absorbing, original read.
Here's a video of Levithan talking about Every Day: