Understanding History

I'm not a great student of history, never have been. But I don't know if it's as I get older or just as I understand more about the world around, but I'm increasingly interested in understanding history, particularly 20th century European history.

On our recent trip to Barcelona I was intrigued by the presentation of Catalonia's history and the strange gaps as they seemed to me. The complexity of European history seems quite daunting, but worth at least a little dip of the toe in the water. 

So, does anyone know of a good book, or have any suggestions about where to start?