Here are some books to get you started...

On Differentiation:

The Differentiated Learner: Responding to the Needs of All Learners
by Carol Ann Tomlinson

How to Differentiate Instruction in Mixed-Ability Classrooms,
2nd Edition
by Carol Ann Tomlinson

Differentiation in Practice: A Resource Guide for Differentiating Curriculum, Grades K-5
by Carol Ann Tomlinson and Caroline Cunningham Eidson

Differentiation in Practice: A Resource Guide for Differentiating Curriculum, Grades, 5-9
by Carol Ann Tomlinson and Caroline Cunningham Eidson

Differentiation in Practice: A Resource Guide for Differentiating Curriculum, Grades, 9-12
by Carol Ann Tomlinson and Cindy Strickland

Leadership for Differentiating Schools and Classrooms
by Carol Ann Tomlinson and Susan Allen

Fulfilling the Promise of the Differentiated Classroom: Strategies and Tools for Responsive Teaching
by Carol Ann Tomlinson

Integrating Differentiated Instruction & Understanding By Design
by Carol Ann Tomlinson and Jay McTighe

On The Parallel Curriculum Model:

The Parallel Curriculum Model
by Carol Ann Tomlinson, Sandra N. Kaplan, Joseph S. Renzulli, Jeanne H. Purcell, Jann H. Leppien, Deborah E. Burns

The Parallel Curriculum Model in the Classroom (Book 1 and 2)
by Carol Ann Tomlinson, Sandy N. Kaplan, Jeanne H. Purcell, Deborah E. Burns, and Cindy Strickland