On Wednesday Sony released the version 2.0 of their Sony Reader app for iOS. This app has long offered limited support for Epub3, and with the new update the app now supports magazines in Epub3 format. This is particularly useful for magazines which combine a complex layout with carefully placed text (Wired, for example), and the app also now supports reflowable text in Epub3 ebooks. You can find the app in iTunes Japan (it is not available elsewhere).
In related news, Sony has also reportedly released a new reading app which enables their customers to read ebooks in a web browser. According to my source it currently works with Chrome and Internet Explorer (10 and 11), but I don't have info on whether the app works with Safari, Firefox, or Opera.
It looks like this:
To the best of my knowledge, Sony's last ebookstore is region-locked to Japan, and can't be accessed from other countries. It stocks 78,000 titles, including 49,000 comics, 7600 magazines, and other titles.