Tor is garnering well earned kudos for being the first major fiction publisher to cast off DRM from their eBooks (well, they'll be doing it in a couple of months). This means that any Tor eBook you buy after July 2012, from any eBook seller, won't be locked down in anyway. The upside: you'll be able to read your eBook on as many different devices as you like. And you'll even be able to covert these DRM free files to different formats so you can read them on a Nook or a Kindle (if you like).
This is great, but did you know that there are already eBooks in the Kindle store that aren't wrapped up with delicious DRM? It is true, and here's how you can tell if a particular eBook on the Kindle store is DRM-free.
When you're on an eBook's item page on Amazon.com scroll down until you get to the Product Detail section:
If the Kindle book you're looking at is unencumbered by DRM the "Simultaneous Device Usage" section will display "Unlimited."