What's the Name of That Book??? discussion

This is an older book that I read in middle school (2007-2008) although I'm not sure that it was new even then. It is a book about a princess and a prince whose parents are trying to engage/marry them to one another. In the princess's kingdom people can change reality just by willing it and in the princes's kingdom people change their own perceptions, but not reality. The people from the prince's kingdom are wary of the people from the princesses kingdom and the people from the princess's kingdom look down on the people from the prince's kingdom. The princess is opposed to the marriage and escapes into a sort of alternate world ruled by an evil dictator and the prince comes along with her by accident. In the end the prince and princess learn to respect each other's abilities during their fight to return home and become engaged, but don't marry right away as they were initially supposed to. I seem to recall that the cover was yellow, black, and red- though I'm not sure how helpful that is.

Of Two Minds
"Of Two Minds"- it is the first book of a series. I remember the cover you describe too but it looks like it's gotten a new edition.

That's it! Thanks so much.