He never messages first on Facebook?!?

[Spencer]

What do you want in this?

Do you want him to like you?

If so, your best bet is to message him, and hope he isn't immature and uses people.

With that said.
Here some options
1) He might be immature and do the high school thing of thinking it's cool to ignore people -- ie, he's trying too hard. He might be interested in you, or he just might do this to everyone because he thinks he's cool
2) He isn't interested in the sense he wants to hang out forever, but he thinks you're cool as he can talk to you like his friend
3) He is interested but is shy.

Honestly you'll know best -- knowing him personally. If it were me I'd look at what our conversations look like when we actually have them. Are they me asking questions/trying hard -- or is he trying to get to know me. I don't mean him asking generic questions like -- oh how are you doing -- but he asks about ... something that he finds interesting in you.