Here is a message from Terry Pratchett posted on Paul Kidby’s site today:

Folks,

I would have liked to keep this one quiet for a little while, but because of upcoming conventions and of course the need to keep my publishers informed, it seems to me unfair to withhold the news. I have been diagnosed with a very rare form of early onset Alzheimer’s, which lay behind this year’s phantom “stroke”.

We are taking it fairly philosophically down here and possibly with a mild optimism. For now work is continuing on the completion of Nation and the basic notes are already being laid down for Unseen Academicals. All other things being equal, I expect to meet most current and, as far as possible, future commitments but will discuss things with the various organisers. Frankly, I would prefer it if people kept things cheerful, because I think there’s time for at least a few more books yet :o)

PS I would just like to draw attention to everyone reading the above that this should be interpreted as ‘I am not dead’. I will, of course, be dead at some future point, as will everybody else. For me, this maybe further off than you think – it’s too soon to tell. I know it’s a very human thing to say “Is there anything I can do”, but in this case I would only entertain offers from very high-end experts in brain chemistry.

This is very sad news for Terry Pratchett, his family, and his many fans. I was very sad to hear about this – it’s a tragedy for this to happen to anybody, but it’s especially heartbreaking when it happens to somebody as clever and witty as Terry Pratchett is.