Only my point of view .... the specification is the most important materials.
1. Wireless Java: Developing with J2ME, Second Edition
by Jonathan Knudsen (the most upadte J2ME book).
on the concept side (not update as to cover all the exam objectives :-()
2. Core J2ME Technology by John W. Muchow
I go for the Core J2ME + spec path.
[ February 06, 2004: Message edited by: Kelvin Chan ]