I think the most concise and complete writing on the topic of Milton Erickson's approach and theory of change is found in the article "Ericksonian family therapy" below. (It does also deal with hypnosis but gives his work in a developmental framework.
"ERICKSONIAN FAMILY THERAPY" Lankton, S., Lankton, C., & Matthews, W. (1991). "Ericksonian family therapy." In A. Gurman & D. Kniskern (Eds.), The handbook of family therapy, volume 2. New York: Brunner Mazel.
*** [I especially like the 1991 paper immediately above, I think it is the best].
"AN ERICKSONIAN MODEL OF HYPNOTHERAPY" Matthews, W., Lankton, S., Lankton, C. (1993) "An Ericksonian Model of Hypnotherapy," In E. Kirsch, S. Lynn, J. Rhue (Eds.). The handbook of clinical hypnosis. APA.
"ERICKSONIAN APPROACH TO HYPNOTHERAPY" Lankton, S., Lankton, C., Matthews, W. (1994) "Ericksonian Approach to Hypnotherapy," In E. Kirsch, S. Lynn, J. Rhue (Eds.). The handbook of clinical hypnosis, volume 2. APA.
"ERICKSONIAN APPROACHES IN SOCIAL WORK" Lankton, S., Lankton, C. (1997) "Erickson Approaches in Social Work," In Dorfman, R. (Ed.). Paradigms in Clinical Social Work, volume 2. New York: Brunner Mazel.
There is also a statement about his epistemology that will be helpful on the www: http://lankton.com/epist.htm . This aslo has a bibiliography included.