Oh no!
Barthes!! The last time he reared his hoary old post-structuralist head was in
The Thread That Must Not Be Named.
Lal, as always, makes some nice points but I would hasten to add a couple of things to what she's offered:
First, Barthes is rather 'old fashioned' now in lit crit with most theorists having gone on from post-structuralism to other things. Interestingly enough, there's been something of a return to reading texts as actually containing some substantive relation to the 'real': usually along the axis of politics (postcolonial reading, neofeminism, ecocriticism) and in each of these the authors are returning from the dead.
It's also important to keep in mind that Barthes was writing a rhetorical piece that was meant to garner and cause a reaction -- which it did. At the time the essay appeared the world of lit crit was still suffering from the Romantic notion that the meaning of any text springs wholly and solely from the Intent/Genius of the Prophet-Author. The reader in this model was a poor second cousin who comes along after the fact, sits passively at the knee of the author and sees what he (and it was almost always a he) had to tell about the world. Breaking through this mode of thinking and creating a more interactive role for the reader -- making the reader more active in the process -- was Barthes' aim, and in that he succeeded admirably.
I make these points because from my view of Tolkien and Barthes they are not really that different in their approach to what Barthes calls the "author-function". Obviously, he never argued that there is no author to a text, only that the person who writes a text is not its Author (i.e. sole and original creator, the originary point from which it springs as the world did from the Mind of God); instead the person who writes the text fulfils the author-function of acting as a screen or mediator between the myriad and infinite number of texts and experiences and social forces that he or she has moved through, on the one hand, and the reader on the other. This is much like Tolkien's view in some interesting ways, insofar as while Tolkien argued that in fairy story the writer acts as the subcreator of a new world, the 'meaning' of that world is not something that springs from the writer. The meaning of the subcreated world comes from the underlying truths of the primary world that the writer acts as a transmitter of or for.
So Barthes and Tolkien are alike in how the author functions: for both of them you have something like this...
the "real" world/Primary world --> writer --> the text/Secondary world --> Reader
Neither of them thinks that the meaning of the text is contained by the writer, and both of them argue forcefully for the reader's active and participatory role in the reading act. The 'point' of reading for both is that the reader can engage with a text and then use that engagement to move toward an understanding of the forces that are at play in the text and which shaped it
through the writer. Neither sees the writer as a prophet, but as a mediator.
Where they do differe significantly is in their perceptions of what constitutes that "real" or Primary world. For Barthes, the real world was sociological and materialist; for Tolkien it was pschological and religious. So while they both agree on what the "author function" is they disagree over what that function is about. For Barthes, the reading act immerses the reader in sociological and material historical forces (which are protean, multiple but, ultimately, analyzable), while for Tolkien the reading act immerses the reader in psychological and religious truths (which are stable, singular and, untimately, an ineffable mystery to reader and writer alike).