iBooks on the iPhone

At Apple’s (AAPL) event this morning in Cupertino, Steve Jobs announced that–with the advent of iPhone OS 4–iBooks, the iPad’s formidable e-book reader, will also be available on the iPhone. Says Jobs, “Its a delightful ebook reader, and you can buy the books once and read them anywhere.” Where does that leave Amazon (AMZN)?

The Seattle-based online bookseller currently lets iPhone users read Kindle titles on their devices, and this constitutes a large percentage of iPhone e-book reading, but iBooks will soon be standard on all iPhone OS 4-powered devices. This may up the ante on Amazon’s Apple offerings.