One book about Belfast Celtic that is easy to obtain is 'Paradise Lost & Found' by Padraig Coyle. It's on Amazon US for a couple of bucks in paperback:
http://www.amazon.com/Paradise-Lost-...9424034&sr=8-3
I read it a while ago, it's a good general history of the team, and the circumstances of their demise.
There's an excellent website about the team here:
http://www.belfastceltic.org/index1.html
There's a list of other books about them there too.