Question

What is Natya-Shastra a handbook of?

Answer 1

An encyclopedia on dance, music and theatre. Nãtya Shãstra written by the sage Bharata or Bharatamuni is the most elaborate treatise believed to be written during the period between 200 B.C and 200 A.D. 
It is written in Sanskrit language, composed mainly in 6000 Sutras or Verses or Stanzas , incorporated in 36 Chapters. There are some passages, that are composed in a prose form.

Answer 2

It based on the various dance forms .                                                                 Natya = dance or drama                                                                                      Shastra = science of technique .