It includes a Fritz 9 engine version and some improvements of the interface, compared to version 8 (Chess960 support, multiboard kibitzing on the server, chat emoticons...):
http://www.chessbase.com/shopd/product.asp?pid=423
(It looks like there are no english versions of the Fritz for Fun editions?)
If you already have the full product Fritz 9 or even Fritz 10, I think it will not make sense. But I didn't have Fritz 8 and bought the "for Fun" Edition 4 which has the last Fritz 8 edition (most probably identical to F8 Bilbao). It doesn't include the Fritzbook though, but a smaller one. Some time after the FfF. 3/4 releases each, also CD jewel case editions for ~10 Euro were released, with F7 and F8. I do not know in which countries they are available and in which not, but in Austria and Germany they appeared in supermarkets (but not on the CB. website). I hope for Fritz 9 to come for that price too, but I am not sure.
