I'm currently reading a book by Justo Gonzalez called The Story of Christianity. It's pretty light weight, just barely introducing themes and characters before moving on to the next topic. But, it has reawaked my interest in the subject. I was a religious studies minor in college and quite enjoyed my history classes in particular.
Just watched TheOOZE.TV interview with Diana Butler Bass. She has a new book out called The People's History of Christianity. It looks like a pretty good easy read as well so I'm going to check it out. I enjoyed the interview and look forward to checking out the book.