Light Transport
Physically Based Rendering: From Theory to Implementation
Comprehensive reference on physically based rendering techniques
The rendering equation
The classic Kajiya rendering equation paper introduced the "rendering equation" and the path tracing algorithm
Robust Monte Carlo Methods for Light Transport Simulation
the Academy Award-winning Ph.D. thesis by Eric Veach. It starts from bidirectional light transport algorithms and introduces multiple importance sampling and Metropolis light transport
Advanced Global Illumination
An advanced book focused on light transport theory for global illumination.