There's also a cool Borges short story where he writes of a story with nine different beginnings, that slowly combine three different middles, and the same ending.

I don't know that one... anyone have a title? I'd love to read it.

Also, anyone interested in writing an adult CYOA book should check out Kim Newman's Life's Lottery, which is an interesting attempt to do just that. (Not that there's not room for more, mind...) I think it was only published in the UK, so it's a bit hard to find in the US, although you can find used copies.

(oh, and that not-quite-double post above? oops...)

...There are a number of these out there; I tried posting links but I think it got my message caught in the spam filter. Alas.

But there are some others, although only a few as nice as this one. You can find a whole bunch at Demian's Gamebook Web Page, although those are hand-drawn and can be hard to read. I've seen quite good ones of The Cave of Time and Third Planet from Altair; anyone who wants a link can email me (sef23 - plus that little symbol for at, you know the one - .cornell.edu) and I'll email you the links.

There are a surprising number of these maps around; a few good ones include this one of the Cave of Time:
http://classweb.gmu.edu/msample1/fall2005/343/caveoftime.jpg

And this one of the Third Planet from Alter:
http://www.ethblue.com/cyoa/

There are also a bunch at Damien's Web Book Page, here:
http://www.gamebooks.org/index.php

--although they tend to be hand-drawn and hard to read.