Here are a few resources where you can find out more about theories.
Inkson, K. (2006) Understanding Careers: The metaphors of working lives. Sage Publications.
An up-to-date and readable overview of the main movements in career theory. If you only buy one theory book, this is it.
Swanson, J.L. & Fouad, N.A. (2009) Career Theory and Practice: Learning Through Case Studies. Sage Publications.
Takes a number of key theoretical approaches and applies them to actual clients. Excellent for practitioners.
Arnold, J. (1997) Managing Careers into the 21st Century. Paul Chapman Publishing.
A bit dated now, but contains a very clear and readable section on classic career theories.
Sharf, R. (2009) Applying Career Development Theory to Counseling. Wadsworth.
This is a standard textbook for many career qualification courses. It’s a bit lacking in some of the more modern theories.
For the devotee
Arthur, M.B., Hall, D.T. & Lawrence, B.S. (1989) Handbook of Career Theory. Cambridge University Press.
Athanasou, J.A & Van Esbroeck, R. (eds) (2008) International Handbook of Career Guidance. Springer.
Brown, D. & Associates (2002) Career Choice and Development (4th edn). Jossey-Bass.
Brown, S.D. & Lent, R.W. (eds) (2004) Career Development and Counseling: Putting Theory and Research to Work. John Wiley.
Gothard, B. Mignot, P., Offer, M. Ruff, M. (2001) Careers Guidance in Context. Sage Publications.
Kidd, J. (2006) Understanding Career Counselling: Theory, Research and Practice. Sage Publications.
Peiperl, M., Arthur, M., Goffee, R. & Morris, T. (2000) Career Frontiers: New Conceptions of Working Lives. Oxford University Press.
Watts, A.G., Law, B., Killeen, J., Kidd, J. & Hawthorn, R. (eds) (1996) Rethinking Careers Education and Guidance: Theory, Policy, and Practice. Routledge.
Palmer, S. & Whybrow, A. (eds) (2006) The Handbook of Coaching Psychology: A Guide for Practitioners. Routledge.