According to the iPhone Dev Blog, the Chronic Dev Team untethered jailbreak for iOS 4.2.1 has been incorporated into jailbreak tool, PwnageTool 4.2. PwnageTool supports iPhone3G, iPhone3GS, iPhone4, iPhone4-Verizon, iPod touch 3G, iPod touch 4G, iPad, and AppleTV 2G.
PwnageTool also includes two very recent improvements to the 4.2.1 JB: iBooks was just fixed by @comex and @pushfix last night so that it works as intended on DRMed books, and the wifi problem on AppleTV 2G was fixed by @nitotv, @DHowett, and @saurik. Both of these fixes will also be available in upcoming Cydia package updates, so if you’re already jailbroken you can wait for those updates rather than restore and jailbreak again.
Other unofficial mirrors are available here...
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This iBook fix update was expected to be held off until the iOS 4.3 jailbreak PwnageTool.
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