Are you in the Arts? I think that in the Sciences its more usual to produce a series of journal articles, rather than one publication (in which case publisher deals and royalties etc don't exist!). However, I did sit in on a session at a conference where a guy from a publisher was talking about monographs, but if I remember rightly (I apologise I didn't listen that intently as it didn't seem relevant to me!) he was talking about publishing during a post-doc etc. He did say the whole process took a while, so I suppose it can't hurt to do it early. However, is a year too soon? They'll want a pretty firm proposal that will probably go to peer-review, and if your PhD conclusions change...
In Europe (especially the Netherlands) science PhDs, or a collection of papers from a PHd are often published in a nice monograph-style publication. I've got two on my shelf, and I think they're really useful. I think the University pays something towards it?