Yes, someone was asking about this sort of functionality yesterday.  Except they wanted the visitor to fill out an information submission form — rather than checkout and pay.

What you want is actually a little easier than what they wanted.

The easiest way to do what you want, is to edit the file "single.php".  Where the "add to cart" button is displayed, you would simply disable it from showing (comment it out).  That way everything would display, but there would be no "add to cart" action.

You would also disable the "view cart" links in the header and footer.

That should be about it.