Man, IP v6 isn't coming out for quite awhile now. I don't think that there is going to be any book on IP v6 while it's still in development. All I got to say is when it comes out, I'm screwed. I just got the concepts of IP v4.
There are books on IPv6, but I haven't read any, so I can't make a recommendation. IPv6 can be and is implemented many places already. There is already IPv6 implementations of routing protocols, DNS, etc. I think this will all be transparent to the end user for the next several years, but if you work for an ISP, a huge corporation, or the government (especially the government), you might as well get ready for it.