Information needed for the examination is available in standard texts and journals dealing with clinical neurophysiology. Listed below are some helpful resources:

AANEM's Suggested Reference List - list of study materials assembled by the AANEM 
AANEM Educational products and publications
AANEM’s Guidelines for Ethical Behavior Relating to Clinical Practice Issues in Electrodiagnostic Medicine 
Electrodiagnostic Self-Assessment Examinations (EDXSAE)

A recent study published in the American Journal of Physical Medicine & Rehabilitation (2008,87:221-3) found "There is a statistically significant relationship between percentage of correct answers on the Electrodiagnostic Self Assessment Examination and subsequent percentile ranking on the American Board of Electrodiagnostic Medicine Certification Examination, with higher EDXSAE scores predicting a higher ranking on the ABEM examination."

Please note, however, that the ABEM does not necessarily consult the material on this list in the development of examination questions.