With the update, iBooks for Mac hits version 1.0.1 and, according to Apple's release notes, brings unspecified "bug fixes and performance improvements" to the newly-released OS X title. This is the second Mavericks app to be updated today.
Earlier, Apple pushed out an update for Mavericks Mail, which takes care of problems associated with Gmail and custom folders. The company also issued an EFI update addressing keyboard and trackpad freezing issues seen in late-2013 13-inch Retina MacBook Pros.
Apple first brought its iBooks platform to the Mac with OS X 10.9 Mavericks when the operating system launched in October. The software allows users to read e-books purchased through the iBookstore, as well as buy new books directly from their desktop or laptop. Titles are synced across iCloud, and can be automatically pushed to compatbile iOS devices.
The iBooks 1.0.1 update is available now and can be downloaded via Software Update.