iBook is best read app in iOS, Kindle app for iOS is slower than iBooks app at the synchronous reading. the iBooks interface is more like a library. And you will feel that the books are really on your bookshelf. So this guide will show how to read DRMed Kindle books in iBooks.
Download your kindle books in amazon app Kindle for Mac/PC
If you don’t install amazon app Kindle for Mac, please download Kindle for Mac and launch it at first. And register it with your Amazon account.
run Kindle for Mac,Go to library of the application software sidebar
right-click ebook title to download it to the local computer.
Convert kindle books to epub for iBooks
It seems impossible that we can get protected Kindle books into iBooks. Firstly, mostly purchased Kindle books (.azw4, .prc, .azw3, etc) are protected from DRM. Secondly, the Amazon kindle main formats are MOBI and AZW. But iBooks doesn’t all support these formats except for epub.

Run eBook Converter, click Import ebook button on toolbar to import kindle ebook download in local hard drive by Kindle for Mac,
Change Output format to “epub format” at Output options tab at bottom.
select ebook you want, click “Convert” button, it takes a while and new epub saved in output folder.
Read converted kindle books on iBooks
Run the iBooks application on Mac. Navigate to “File”->”Add to Library” and it will pop up a window for us to load new epub file into iBooks.