Linear and Geometric Algebra, by Alan Macdonald: http://www.faculty.luther.edu/~macdonal/laga/
Vector and Geometric Calculus, by Alan Macdonald: http://www.faculty.luther.edu/~macdonal/vagc/index.html
Application to physics: New Foundations for Classical Mechanics by David Hestenes: https://books.google.com/books/about/New_Foundations_for_Cla...
Geometric Algebra For Computer Science by Dorst, Fontijne, and Mann: http://www.geometricalgebra.net/index.html
In the docs section, the Geometric Algebra Primer by Jaap Suter is excellent. http://www.jaapsuter.com/geometric-algebra.pdf
edit: link http://www.astro.umd.edu/~jph/GAandGC.pdf
https://g.co/kgs/ciKXVS
Author(s): D. J. H. Garling Series: London Mathematical Society Student Texts 78 Publisher: Cambridge University Press, Year: 2011 ISBN: 1107096383
Linear and Geometric Algebra, by Alan Macdonald: http://www.faculty.luther.edu/~macdonal/laga/
Vector and Geometric Calculus, by Alan Macdonald: http://www.faculty.luther.edu/~macdonal/vagc/index.html
Application to physics: New Foundations for Classical Mechanics by David Hestenes: https://books.google.com/books/about/New_Foundations_for_Cla...
Geometric Algebra For Computer Science by Dorst, Fontijne, and Mann: http://www.geometricalgebra.net/index.html