Just register both Kindles to one acct. Then you can share books. Just use the Manage My Kindle page on the acct to download purchased books to the second kindle. I do ths all the time with my kids' kindles.
You can, but it has to be someone you don't mind having your amazon password... At that point they can register their device with your account and re-download everything you have for free. The only downside would be that they can't access their purchases and yours at the same time... and of course they'd be able to buy books with your money, lol. When they are finished with the book you wanted to share they can re-register to their account.. good luck!
You actually can both read it at the same time, all you have to do is after synchronizing both devices to get the content on both kindles you would go to "my account" and "un-synchronize" after one of you is done reading the book, re-sync so you would both get the latest downloads and messages!
Another way to share via email, which is good if you don't want to give access to your Kindle account.
1. Connect your Kindle to your computer using the USB cord.
2.When the Kindle window opens on your computer (mine shows up in the lower right corner as "Kindle F:", as if I'd connected a thumb drive), open the "Documents" folder, which you'll see has all your Kindle book files.
3. copy the Kindle title you want to share onto the desktop (the Kindle icon looks like a blue book with an "a" on it).
4. Create a new e-mail to the person you want to send the Kindle book to. Attach the Kindle Book file to your email. Most kindle books are small in file size, about 400k.
5. Send the email. The recipient can download the Kindle book to their desktop from the email. Then attach their Kindle with the USB cord, and add the Kindle book file to the Kindle Documents folder.
Once you add a Kindle book file to the Documents folder, after disconnecting the USB, restart your Kindle and the new book will appear in the list.
although you cannot directly transfer books from kindle to kindle you can associate both kindles to one amazon account and then the archive will feed up to five or six devices so in essence if you buy a book from amazon it go to the archive you then may each download from the archive
Amazon has just enabled the loaning of books!! Go to "manage my account" and look at your purchases. If you expand them and there is a button "loan this book" you can send it to anyone whether they have a kindle or not. If you purchase a book, look in the description and it will tell you that Lending is enabled. I am guessing that publishers will let the sharing take place for the same books on the kindle as the nook.