Marketing A Book as a Prequel?

Okay, so I'm aware that a book you query needs to be standalone, and the first book of a series has to be strong in order to pick up the next book.

In the meantime, I'm working on what I plan to be a two book "series." The whole story is too long to be one book, but as three books would probably be too short. The genre is YA semi-dystopian adventure.

The rough draft for both books has been written. I'm currently sitting on the third revision of book one in order to give beta readers a chance to critique it and to distance myself from it.

I recently started editing book 2 (note, book two was written first and book one was written second), and I've realized it has a closer voice to what I originally intended, and to me sounds more interesting. Also, I feel that I could make it stand-alone with occasional allusions to the events of book one.

So I'm wondering, would it make sense to try and market book 2 first, and suggest that there is a prequel? Or should I stick with book one, which sets up the scene and explains a lot of the why-something-happens in book two?

I'm thinking I'll ask the beta readers this once they've had a chance to read book one.

Any thoughts?

Hmm, that does make sense, and I hadn't really thought about that. I guess I'll see how the second one's going and then decide from there.

Any other thoughts on the subject matter?

Alright, I'll see how it goes, then. Thanks.