Hi!
I think the references would vary according to the sub-features eg. BGP-VPNs, VPLS etc.
But in general, especially for MPLS and the L3 VPNs, I have found the following book very useful :
Cisco Press - MPLS And VPN Architectures, Vol I and II.
The following book gives detailed configurations, scenarios and some explanations on some other architectures. :
Cisco - MPLS Configuration on Cisco IOS
Software(2005).chm
I personally have found this book very helpful in actual configurations.
Specifically for L2 MPLS vpns, the better reference is
cisco-press L2 VPN Architectures.
Also when I had started with mpls, I had found the CCIP MPLS PPTs very useful, i.e. if you dont want to read through all the pages but get the understanding.
Hope this helps.
Cheers!
Niranjan
