Two non-fiction works come to mind immediately:

Autobiography of Dying by Archie Hahn, a newspaper editor with ALS, and
Diary of a Dying Man by William Soutar, a Scottish poet.

The former is long out of print, but the latter is available from Canongate,
a
Scots firm that is distributed in the US.

Also, a fictional work worth looking at is Eighty-Sixed by David Feinberg,
about a young man dying with AIDS (which Feinberg died from shortly after
the
novel was published).

In fact, the AIDS epidemic has produced a number of excellent works in this
vein, although the Feinberg is the only one that comes to my mind
immediately.

George Robinson