Explain the factors that distinguish a good publishable literature review from a poor literature review.

The best place to look for factors on what defines a
publishable literature review might be in the publication guidelines for respected
literary journals.  Each journal will produce a set of guidelines to help authors of
literary criticism articles in the submission process.  Each journal has a set of
standards that guide article length, titles for criticism, theoretical perspectives,
etc. 

Also, become familiar with the styles of literary
criticism articles that are published in the field.  University and college libraries
have these in their online databases--Academic Search Complete or Premier provides many
journals in literary criticism. 

That said, factors that
seem to be standard in published articles are a clear theoretical perspective, a
critical position on a text that is nonstandard (i.e. its a given that The
Great Gatsby is a story about illusion vs. reality so who would publish an
article about this unless the writer has something special to say about it), and heavy
engagement with and familiarity of the text.

The
Explicator is one of my favorite literary journals; you might consider
reading a few of the articles in the journal as an example.