It's perhaps a bit of a stretch to imagine that everyone knows what a Kindle is so here's a brief explanation.
It's a handheld wireless reader device for books. It's made by Amazon, sold only - as far as I know - in the US, and it's gimmic is that you no longer need to connect the reader to a PC to add content to it, but can receive content wirelessly.
How that fits with the fact that you can buy Kindle editions of books on-line at the Amazon.com site is beyond me and it's even more beyond me why anyone would want to pay the prices (= standard Amazon real book prices) that Amazon wants for them, but there we are.
This note is naturally to say that I've now discovered a bunch of six Kindle editions of SharePoint (2007) books, so I've added a Kindle group (at the bottom) to the books list here
http://wss.asaris.de/sites/walsh/Lists/WSSv3%20FAQ/V%20Books.aspx
where I list the ones that are already out (another is listed but not yet out and has no pricing, so I'll keep checking for newly released ones on a regular basis).
So if you want to see which books publishers thought were worth putting out in a Kindle edition, look there. Also be warned. I don't list one SharePoint book that is out in a Kindle edition because it is the *2003* version of an almost identical-looking 2007 book (Wrox - Beginning SharePoint 2007 Administration)