Since you are new to MPLS, it would be ideal, if you can start with MPLS and VPN Architechtures. This will take you through the base building process and also expose you to advanced topics.
After you are through with the book you can then go onto MPLS VPN Design and Implementation. This book will explain basics plus also good amount of details in terms of implementation specifics and lots of sample configuration with topologies. So that your theoritical understanding would be further emphasized.
Also when you go through these books you can come back to this URL and explore all that is there to MPLS
http://www.cisco.com/en/US/tech/tk436/tk428/tsd_technology_support_protocol_home.html
HTH-Cheers,
Swaroop