It may or may not be against the iBook EULA, which might make you in breech of contract, or make you guilty of using a computer system without agreement.
Unfortunately, after looking into things it seems that the law in Sweden also prohibits breaking DRM. There is a provision that if I am unable to otherwise use the content, I am allowed to break the copy protection. However, the law also prohibits making and spreading software that is capable of breaking copy protection, so that sort of contradicts that escape route (since they can just say that the illegal act was figuring out how to break the copy protection, not the actual breakage).
In swedish, from the swedish government: http://www.sweden.gov.se/content/1/c6/05/07/29/96c6bfb1.pdf
It's a sad state of affairs. :(