Apple has seeded the latest beta of OS X Mavericks to developers, which this time includes iBooks for Mac, reports 9to5Mac. This is the first Mavericks build seed to include iBooks for Mac. According to reports, the app doesn't look much different than what was previewed at WWDC this June.
The iBooks app has the same features as the iOS version, functioning as both a store and a reader. OS X Mavericks will ship this fall.