Apple has released OS X Mavericks Developer Preview 5 today following the release of the fourth preview two weeks ago. The update is available via the Mac App Store for registered developers already on the Mavericks beta, and a direct download is available in the Mac Dev Center. Apple’s iBooks for Mac app has been included for the first time in this particular beta release. General stability and performance issues have also been addressed.
The eighth beta of OS X Mountain Lion 10.8.5 was also seeded today. 10.8.5 will likely be the last Mountain Lion update to come out before Mavericks is released to the public this fall.
Apple has been generally sticking to a two-week release cycle for Mavericks and iOS 7 betas this summer, despite the Dev Center outage. Mavericks is continuing to get more stable with each preview release, and the finishing touches are being put on 10.8.5.
Source: Apple