Have you taken any classes? I found that several of the best refrences comes from the classes. That being said I also have some on hand here the ones that I refrence most other than the class room books are Residential Sales Comparison Approach and Appraising Residential Properties (3rd Edition). Both of these are from the Appraisal Institute. I'm sure some of the older and wiser appraisers on the forum know of several other books out there. I would also like to here what they have to say. Since I'm always looking to add to my collection of books.
I am presently taking an Appraisal class at a local college and the instructor is using his own book that is really very good. It is also very interesting as well. The title is Residential Real Estate Appraisal, third edition by George Miller and Katy Gallagher. The ISBN # is 0-324-14054-1.