As far as I remember, there were problems with ibooks and the jailbreak for 5.x.
So there was a fix in cydia for that.
Then something was changed and ibooks was working properly.
Now ibooks 2.1 is there. Is it save to update or is ibooks 2.1 producing problems on jailbroken 5.0.1 ipad 1?
Is there a webpage where old versions of free apps are stored?
So somebody can download an old version of e.g. ibooks?