I've recently looked into the services provided by various Print on Demand printers/distributors and opted to have my colour print catalogues produced and distributed by Lightning Source:
Lightning Source (LSI)
I've read good things about the quality of LSI output and customer service. Their distribution networks are especially attractive. The LSI submission process though is rigorous. While they provide a great deal of documentation to help one get things right, a great deal has also been written on how to move through the submission process without issue, and particularly on how to avoid common pitfalls resulting in rejected submissions and costly reproofing. Here is just one of many examples:
Self-Publishing Review | Blog | Publish With Lightning Source
I'd be interested if any of you have dealt with Lightning Source and have any pointers on the submission of books containing *colour* plates, especially on getting your CMYK images just right.