If the display doesn't support more than 1024, then a hack will be useless. And I don't think there are any iBooks which have diplays with higher resolution.
There is, however, a hack, which allows to run at a higher resolution on an external display connected to the iBook. This is a feature of the hardware, which has been disabled by Apple in software and thus can be restored with a hack. I don't remember the name of this hack though.