Yesterday Apple released OS X Mavericks Developer Preview 5, build 13A538g, just 8 days after the release of Developer Preview 4. Developers who are already running Mavericks can get the 1.08GB update through the Mac App Store, while those who are looking to install it for the first time will need to log in to the Apple Developer Portal. This build doesn't seem to bring too many obvious changes, other than the expected performance improvements and bug fixes, with the exception of the inclusion of the new iBooks Mac app. iBooks lets you read the books you've purchased from the iBookstore on your Mac, just as you can on your iOS devices. As for the rest of the world, OS X Mavericks is set to launch this fall, bringing features like iBooks, Maps, Finder Tags, enhanced multi-monitor support, tabbed Finder, and more to Apple's desktop operating system.