Curves and Surfaces in Geometric Modeling: Theory and Algorithms
The NURBs Book (Monographs in Visual Communication) - A NURBS book for software developer, it covers the theory and also the practical side.
NURBS: from Projective Geometry to Practical Use - This is more useful for learning the mathematical foundations of NURBS than for programmers looking for a reference book on practical algorithms or applications of NURBS.
An Introduction to NURBS: With Historical Perspective - This is a good textbook for the theory and maths of curve and surface computer modeling.
Rhino NURBS 3D Modelling. Rhino is a 3D Modelling program, this book explains how to use it.