I'm not a lawyer (so correct me if I'm wrong) but here in Poland there is a law that allows you to reverse engineer a product that you bought to make it work on your hardware (e.g. you bought a windows only program but want to make it work under Linux)
So I I buy a book that can't be viewed on device of my choosing (e.g. because of DRM) then I'm free to do whatever I want to the product to make it work on my hardware.
No EULA can be above the state law.
In the UK at least, there are a variety of reasons why a contract, or at least part of it, may be unenforceable - such as unfair/unreasonable terms, things that contradict the law, or the particular terms were considered "hidden" (e.g. too small a font size, or an important clause is buried in page 27 of an unrelated section).
EULAs are technically legally binding contracts, and breaking them leaves you liable in civil court.