Q: I live in Spain, but want ibooks in English, how do I do it?

Go to a bookstore or see if a different online vendor is licensed to distribute books in English in Spain. If you live in Spain then you can only get what the Spanish iTunes Store has which is probably books in Spanish.  You can't use the iTunes Store in a different country if you are resident in Spain.  The iTunes Store in a country is intended for use only by that country's residents, and only while they are in the country. To use the iTunes Store in a country you need a credit card (or other card type if acceptable in a country) issued in that country, billed to an address in that country, and also be physically present in that country when using the store.  You are also restricted to waiting 90 days between country changes.

E.g., "The iTunes Service is available to you only in the United States, its territories, and possessions. You agree not to use or attempt to use the iTunes Service from outside these locations. Apple may use technologies to verify your compliance." - http://www.apple.com/legal/itunes/us/terms.html#SERVICE (and may delete an account if you are violating the terms).