The rai-f FAQ says:
Several papers on IF design and theory are available via anonymous FTP from
<ftp://ftp.gmd.de/if-archive/info/>
[...]
Graham Nelson's treatise on writing a work of IF, "The Craft of Adventure",
is highly recommended. This is currently in its 2nd edition and is
available either as plain text or in a TeX version. Get either the file
`Craft.Of.Adventure.txt' or `Craft.Of.Adventure.tex'.
Read the FAQ 8) (it's available as
<ftp://ftp.gmd.de/if-archive/rec.arts.int-fiction/FAQ>).
-- Jools Arnold jools@arnod.demon.co.uk