Hi there,
Here you go these are the books that i've used to understand MPLS well and pass the exam:
1.MPLS Fundamentals
Luc De Ghein, CCIE #1897
2.MPLS and VPN Architectures
By Jim CCIE #2069 Guichard, Ivan CCIE #1354 Pepelnjak
3.Implementing Cisco MPLS Student Guide
HTH,
Mohammed Mahmoud.
