Reddit mentions of MPLS Fundamentals

Vendor neutral and probably the best/most frequently recommended book:

MPLS-Enabled Applications: Emerging Developments and New Technologies

Very good Cisco-centric MPLS book:

MPLS Fundamentals

The gold standard, or so I hear, for L2VPN (I believe it's Alcatel/Juniper heavy):

Designing and Implementing IP/MPLS-Based Ethernet Layer 2 VPN Services: An Advanced Guide for VPLS and VLL

I actually just started reading MPLS Fundamentals from Cisco Press. I'm several chapters in and so far I've found it to be clear, comprehensive, and very informative.

>I've played around with MPLS in lab environments, and got it working but only in its most basic form, and without truly understanding what's happening in the background.

mpls ip under global and interfaces <-- MPLS EXPERT



Here's a good PDF overview from NANOG titled "MPLS for Dummies."

I also enjoyed CBT Nuggets MPLS Fundamentals course.

Then this book -- MPLS Fundamentals -- is highly rated. (at least on Amazon)