What are the main points raised in Barthes' the death of the author and from writer to text?

This is part of the general
Deconstructive/Post-structuralist project: that is to decenter the source of meaning, to
show the multiplicities of meaning and interpretation. For Barthes (or Derrida), there
is no source: there's only destination. 

When Barthes says
the "birth of the reader must be at the cost of the death of the Author," he means that
the meaning of a literary text (or any writing really) is not limited to the Author's
intent. Previous historical understanding of an Author are: 1) the Author as a
communicator, a poet, or a shaman, one who is a conduit of some Truth from God or
Nature, and 2) the Author gives birth to a text, creates it; thus, all understanding of
a text ultimately leads back to the Author, the Creator of the text and therefore, its
meaning. 

Notice that Author is capitalized in this essay
and "reader" is not.  This is because previous conceptions of the Author are similar to
God in creating.  If the Author has that kind of "author-ity" over a text, the meaning
of the text is only of His/Her doing.  Writing is the medium and the reader is just the
passive receptacle for drinking in information the way a computer is programmed to
perform functions. 

Barthes sees the author in a different
light. For Barthes, the Author (and the modern New Critic who is more like a shaman
trying to understand that Ultimate, Transcendental Signified Meaning of the Author/God);
the Author is not the origin of the text's meaning. Barthes replaces the word Author
with scriptor.  The scriptor does not precede the text as an all-powerful
Author/Mother/God-Creator would.  The scriptor is simultaneous with the text as if
he/she were a character him/herself.  The scriptor, with respect to a text, is more like
an interpreter of history and culture, or like a chemist who takes chemicals
(analogously, ideas) and mixes them together: the result is the text/mix. Then he shows
what he's mixed to the reader.  What is the point of the mixture(text)? The point(s) or
meaning(s) are not limited to, or originating from the Author(scriptor). The reader, the
destination, is where the multiplicity (freedom) of a text's meaning is manifested.  The
reader(s) has the power to read the text in various ways; to limit the meaning to just
one Original Creator(Author) is not really a slight on God; rather, the limiting of that
meaning would be like saying, 'as soon as the text is created, it ceases to grow because
the meaning is 'fixed' and is only attributable to the Creator."   - As if the Author
were a parent, the text his child and the Author spent his entire life being the Only
influence on the text/child, therefore making it impossible for the child to grow or
interact with others (readers). 

But for Barthes, the
scriptor is not like a parent and the text is not like a child. Thus the meaning(s) of a
text is not limited to either.  The child is the reader.  "The birth of the reader must
come at the death of the Author." In a twisted but logical sense, the reader gives birth
to a text by reading it. The reader liberates it (and him/herself) by not limiting it to
some Original meaning.  This is part of a general philosophy that a reader or student is
not some passive vessel waiting to be programmed but an active participant in the
construction of meaning and history.