QI will be releasing two books later this year. The 4th October will be the UK release date for The Book Of Animal Ignorance (pictured) which is the sequel to the 2006 Amazon global Christmas no1 bestseller The Book Of General Ignorance.
Also due for release on 1st November will be The QI Annual, 2008. This will be the first QI annual so make sure you buy two - one to scribble away in and the other to put in a sealed plastic bag until it's worth more than a Blue Peter first edition.
Read more about the two releases here (opens as a .pdf file)
Meanwhile The Book of General Ignorance will go on sale in the USA (with a different cover) from 7th August 2007. You can pre-order a copy from Amazon.
Edit (Mon 23/04): Coming later this week, A Guide to QI Recordings.