Can one appear for law with coaching,only by taking reference books..... which will be better - coaching or following a guide book

That depends that how much you can balance the studies by self. Know the paper pattern and syllabus and then try to give previous year tesrs. After giving the tests you will get an idea if you can study by self or not.

Further studying by self is a good idea but you have to be very sure about this. SOME OF THE BOOKS ARE:

The Pearson Guide to the CLAT (English)

Word Power Made Easy New Revised & Expanded Edition (English) by Norman Lewis

Manorama Yearbook 2017 (English)

Analytical Reasoning (English) by M K Pandey

CLAT Solved and Practice Papers (English) by AP Bhardwaj

Universal's CLAT Solved Papers

and there are more..

Hope this helps.