I get that question a lot. Now that my Tymber Dalton fiction will be releasing exclusively through Siren-BookStrand, I know I’ll be getting it a lot more frequently.
You CAN buy my books for your Kindle (or nook or whatever) straight from Siren-BookStrand. And if you have a Kindle, all you have to do is go into your Kindle account on Amazon and allow your device to get emails from Siren. And log into your Siren-BookStrand account and plug in your Kindle’s email address. Then, when you buy books for your Kindle from Siren, they’ll be automagically sent to your device.
And if you don’t like that option, simply buy the books in your format, download them (all browsers have a Downloads history, in Chrome and IE, it’s Ctrl+J) and then use your USB cable to drag and drop them into your Documents folder on your e-reader. (Or whatever the folder is called on your e-reader.)
Easy! And that way, you don’t have to wait weeks for the book to release on Kindle/nook/wherever.