Earlier, the iPhone Dev-Team released an updated version of RedSn0w for both Mac and Windows. This update (0.9.10b5) overcomes the jailbreak detection by iBooks that would cause some images to not display properly.
According to the Dev Team’s blog:
Redsn0w version b5 incorporates yet another fix for iBooks, this time involving DRM. @planetbeing wrote a utility called “crazeles” that overcomes jailbreak detection by iBooks that would cause about 10% of images to show incorrectly. This fix is similar to the “hunnypot” fix that @comex wrote for the 4.x jailbreak. As usual, you can choose toinstall the fix either by re-running redsn0w over your existing jailbreak (de-select Cydia if you do that), or by installing the corona package from Cydia (it’s the same set of files no matter which way you choose).
If you don’t want to use RedSn0w, Corona will be updated shortly to version 1.0-6 and will fix this iBooks bug. If you would like to re-jailbreak your iDevice with RedSn0w 0.9.10b5 to apply the iBooks DRM fix, you will simply need to go through the Jailbreaking process again, without selecting the Install Cydia option.
You can download this update version of RedSn0w from our downloads page.