If you're asking what I think you're asking the answer is "No, but". . . .John M W Smith said:
No: The book files on your computer are coded for your Kindle for PC app. You cold move them physically (via USB connection) to another Kindle, but they won't work.
But: you can have the book on multiple devices; you just need to go to your Manage My Kindle page, find it under "Books" and send it to the device you want it on. OR, from the device where you want it, go to archive/cloud, find it and download it.
Now, the above assumes we're talking about books you purchased from Amazon. Books that are acquired otherwise, if compatible and not copy protected, can be copied pretty easily. Or use Amazon's Send to Kindle (www.amazon.com/sendtokindle) applet to get them on the Kindles AND have them archived at Amazon as well.
