Just saw the latest version of the Carcosa PDF.
The book itself is extensively cross-referenced, has a proper index, etc.
The PDF takes all of that and links it within the document.
More than that, Eero (design/layout guy for the project) linked every hex on the maps (and the room numbers of the Fungoid Gardens map) so clicking on it goes straight to the entry in the body of the book.
Not that I look at all that many gaming PDFs, but this one is Pretty Damn Spiffy.
The PDF is included in the price of the printed book, and for those not wanting the physical book, the PDF will be available as a stand-alone product on December 11.