i downloaded a book from the itunes store off my macbook how do i read it? on which app? through my iphone?
You can download the iBooks app to your phone and then either re-download the book in that app on your phone (there should be a Store button and then a Purchased tab in the ibookstore for re-downloading), or sync it via your computer's iTunes (using the Books tab) from your Mac to your iPhone. You can't currently read ibooks on a Mac as Apple haven't yet create a Mac (or PC) reader for them - they can only be read in the iBooks app on iOS devices.