IPv6 destination cache in Linux kernel

Hello,

I'm trying to understand how Linux kernel routes IPv6 datagrams. It looks it does it much different from IPv4. While IPv4 uses Destination cache to find out what is the destination IP, MAC and interface index to send packet out, in IPv6 case it uses some destination tree to do that. It also  does not uses that tree in case, if destination address is not on a local network. Is it correct?So, I have a few questions:

1. What are the reasons to rout datagrams differently fromIPv4?
2. Where I could get details how IPv6 stack routes datagrams?
3. Are there around books like "IPv6 Core Protocols Implementation" but with Linux specific details?
4. Any other sources of information about this topic?

Thank you very much,
Mikhail.