Being a new area, there are a large number of manuals available for digital cinema all over the Internet as standard. The first place to try is always the manufacturers own websites, such as Barco or Christie. I’ll try to add more specific links to the different pieces of equipment and their manuals over time.
If you are after more specific digial cinema manuals, similiar to what has existed for film, then the BKSTS has been publishing Training for Digital Projection, which appears as part of the Cinema Technology Journal. It is also worth checking out the excellent manual which has been produced by the Norwegian Film Institute, entitled “The Advanced Projection Manual“, which not only contains information on film projection, but also a large secton on digital cinema and alternative content. It’s unfortuantely not a cheap book, by the time you pay for it’s import into the UK, but is still really worth the money. If you would like more information on the book then this is a good link to have a look at as well.