The internet seems crazy about this quote, but nobody reports a reliable source. Where was it originally written or spoken? (I.e., which book, interview, or essay?)
The quote is likely to be a slight variation of the following:
In a sense, one can never read the book that the author originally wrote, and one can never read the same book twice.
This is from Wilson's The Triple Thinkers (Amazon link). You can see the section of interest in the Preface, page ix. Conveniently, the preview includes that page, so you can view it for free (although without as much context as you might like).
The source can be found relatively easily, with a clear citation, from Wikiquote. It's always worth checking there, or searching through it using Google to see if you can find an entry in Wikiquote—they tend to be quite reliable.