What did edgar allan poe mean when he said a literary piece must create a "unity of effect" on a reader?

a. that every character in the piece will be unified by a common dark secret
b. that everyone reading the piece will be unified by an experience
c. that the effect of all books of one genre be unified by one theme
d. that all aspects of the piece should work together to create a certain effect

i've read it so how can i ?

there are several different forms of presenting this; each has a very specific format. plays have a very simple format; teleplays, for television shows, or screenplays, for movies, have more complex and strict rules for formatting.

drama

the first of these to be written for the express purpose of being performed were created by the greeks. many of our modern terms derive from greek origins.

comedy

in the greek sense, a play that doesn't end in death. in modern usage, refers to a play that is humorous.

tragedy

in the greek sense, a play that ends with the death of at least one of the main characters. in modern usage, refers to a play that doesn't have a happy ending.