A no. of books are available on the subject matter and no end to it.They are good for references. As such if you would have completed leve II certification in above and put up good practical experience in all the methods, U gain more knowledge to write level III.
Further, there are plenty of senior level III inspectors with experience in the field. They conduct coaching sessions and mock up tests ( which are more important) prior to your attempt to get level III.
sridhar
__________________
What we have done for ourselves alone dies with us: while what we have done for other and the society remains and is immortal.
You do need to study to take your ASNT Level III examinations. No question about that. But is my contention you cannot (nor should not) study (only) to become a Level III. Long ago I asked my boss if I could get my Level III in UT. He said he thought it would be OK. I asked if I could go to the ASNT Level III review course. He said that if I needed the course I wasn't ready. That has stuck with me for many years. You are doing yourself and your customers a disservice if you cram to become a Level III. Experience plays a very big role.
That said, the Iowa State University website
http://www.nde-ed.org/EducationResources/educationresource.htm
is a great resource for all Levels (I, II or III). See how you do there.
ASNT offers study guides in the Basic and the major disciplines. These guides are well referenced. One of my favorite books is ASM Volume 17 - a bit pricy, but very complete.
One further thing - don't under estimate the PT exam. It is harder that you might think.