“But in science, there’s evidence,” I argued. “There’s proof.”

“Read it. You’ll see what I mean. You’ll like it.”

I put my hand on my hip and smirked up at him. “How do you know what I’d like?”

Looking back, I can see that this could have been construed as a lame attempt at flirting on my part.

And it worked.

“Oh, I think I know you, Lex,” Steven said, the sound of his voice changing from what it had been a minute ago. “I know what you’d like.”

“Okay,” I murmured, and reached for the book, but he didn’t release it.

“While we’re on the subject, you know what else you’d like?” He cleared his throat and glanced around. We were alone, at least in that particular section of the bookstore. “You’d like to go out with me. On a non-friend type of outing. A date, I mean.”

Boom. A date.

I sucked in a breath. “Is that a question?” I asked stupidly.

“Yes. I mean, would you consider . . . would you go out with me?”

I stared at him. A dozen reasons why this definitely would not be a good idea marched through my brain: This kind of thing would only complicate matters, make a mess. I hated messes. My life was enough of a mess as it was. I was just starting to feel like I had the ground under me again after my parents’ divorce. I needed to focus on school, keep up my perfect grades, get into college, figure out my life’s trajectory. I liked Steven—I liked him so much; that was easy to admit; he was one of my favorite people—but if we were together like that, it would make the other members of our group feel awkward. It would ruin our friendship.

We’d end up hurting each other.

“Steven—” I started to brace myself to say all of the hard things.

“Wait,” he said. “Hear me out.” He extracted the book gently out of my hand and returned it to its place on the shelf, then took my other hand in his. “I know a romantic relationship could be considered risky at this stage. We have a year left of high school before we go our presumably separate ways. I know the purpose of romantic engagement, on a biological level, is for procreation, and neither one of us wants that, of course. But . . .” He glanced down at our joined hands. “That’s not all there is to it. There’s the social aspect, of learning to interact with someone, as a partner, which could be useful for our future experience. And it’s been proven that romantic companionship is good for your health: it promotes the release of endorphins, relaxation, a sense of greater security, and . . .”

We were both blushing by this point. We’re so similar, I thought. When we get nervous, we both start talking like idiot savants.

“You’re babbling,” I observed.

“I know.” He sighed and then kept talking. “I think we could be good together, Lex. I promise I wouldn’t pressure you, about . . . anything, and I won’t have any kind of expectations about what’s going to happen a year from now. I just want to find out what we could be like. An experiment, of sorts.”

I bit my lip. He was making it sound reasonable. Logical. Tempting. That and he was gazing at me with those unbelievably warm brown eyes of his, and his expression said:

PLEASE SAY YES.

“So the experiment would be whether or not there’s chemistry between us,” I said.

He let go of one of my hands to push his glasses back up on his nose, and smiled. “Exactly. A simple experiment in chemistry.”

Which made sense. There was nothing Steven loved more in the world than chemistry.

“So this would entail you and me going on dates,” he continued, moving onto the logistics of how it would happen. “Maybe once or twice a week, or more than that, if you want. Whatever you prefer, really . . . We could—”

“Yes.” The word was out of my mouth before I could talk myself out of it. “I’ll go out with you. Yes.”

“Excellent,” he said, looking so thrilled I thought he might start dancing right there in the bookstore. “You won’t regret it.”

And that’s how it started.

He held my hand during the movie. I sat in the flickering dark stunned by the idea that it had happened so easily, after all this time knowing each other. He asked me to think of him romantically, and I said I would. Just like that.

“This isn’t too weird for you, is it?” he whispered after a while.

“No.” I squeezed his hand. “This is good.”

And it was.

After the movie he drove me across Lincoln to the Oven, an Indian restaurant downtown. He opened the door for me, pulled my chair out as we were being seated, and insisted on paying for dinner.

That was a little weird.

Then he drove me home and walked me to the front door. And at the porch, he stopped.

“Can I kiss you?” he asked hoarsely. There was so much in his expression, and I could read it all. He liked me. He really liked me. He didn’t want to mess this up. He thought it might be too soon, but he wanted to kiss me. He wanted to know that I felt what he felt. It was a real part of the experiment, this kiss. It was:

Does me + Steven + dating = chemistry?

That’s what kissing is supposedly for, on a biological level. It’s a taste test, to see if you’d be a good match.

“Yes,” I said, and stepped closer to him. “You can kiss me.”

Slowly he lowered his head until his lips almost touched mine. He smiled, and I felt light-headed with how much I found I wanted this. I dragged my bottom lip between my teeth to wet it and smiled too. Breathless. Waiting.