hello naveen......

the following are the best books for nata and jee main preparation

1.b.arch nata/jee test by nimish madan

2.nata/b.arch architecture entrance question bank with aptitude mathematics and drawing by ar.ashok goel and ar.arjun kamal

3.steps to architecture by nimish madan

i hope this information is helpful

all the best.

Hiiii

B.Arch exams comprises of Perspective drawing, 2D, 3D and aesthetic sensitivity test. So there is no ideal book from where you can learn and the questions have no fixed pattern as they keep on changing. So don't just refer one book but, go through all books (or at least as many as you can).
Here is a list of few excellent books which you can use.

• NATA & B.Arch Question Bank  by Ar. Shadan Usmani
• NATA & B.Arch complete self study material: entrance examination by  Ar. Shadan Usmani
• A Complete Self Study Guide for B.Arch by P. K. Mishra
• B.Arch Entrance Examination Guide by Surendra Kavimandan
• The Young Architect by Neelam Verma. The complete book for B. Arch. entrance exam preparation.
  
  

Also i will suggest you to keep on solving the sample papers and previous year papers so that you get the idea of how the paper is set.

Prepare well and do good.
All the best