To some people it seems obvious that "religion" suffers a long-term decline (known as "secularization) in a modern, industrialized society. But a few writers, notably Rodney Stark, have made a lot of noise putting the opposite point of view: there is no decline, secularization is a myth. This is a very welcome message to those who believe that we are all born with a thirst for religion.
Others agree that secularization is a reality in Europe, Canada, Australia, New Zealand, Japan, and so on, but claim that the US is the one great exception. Steve Bruce's book is the best available argument for the common-sense theory that the decline is real and that while America is about fifty years behind Europe in religious development, America is no exception.
Although Bruce is from Britain, and a lot of what he says is about Europe rather than the US, he has made a special study of American religion, and he has a chapter devoted to the idea that "America is the exception". He brings together all the most important evidence, from opinion polls, church attendance, and other sources, and most readers will find that the case made for the reality of secularization is irresistible.
There are still some areas where it would be helpful to have more good evidence. For example, in polls, around 40 percent of Americans say that they have attended church in the last week. This number is remarkably stable, going back to before World War II. Recent studies of actual church attendance show that the answers to polls inflate the actual attendance by about 100 percent. In reality, about 20 percent of Americans go to church regularly. So church going is distinctly a minority pastime in America today. But the opponents of the secularization theory claim that it was never any different: according to them, it has always been the case that 20 percent of Americans actually went to church but that 40 percent said they did. Bruce and other sociologists present some evidence to show that actual attendance used to be closer to claimed attendance: the gap between actual and claimed attendance has grown over the decades. But this is a tricky area since it's difficult to measure actual, rather than claimed, church attendance fifty years ago. So there is definitely room for further debate here.
The anti-secularization theorists generally caricature the views of the secularization theorists, rather than describing them fairly. So you will often find anti-secularization writers like Stark pointing out that not everyone went to church in the Middle Ages and that Christianity is not about to disappear completely next week. As Bruce makes quite clear, hardly anyone has ever maintained the views held up as "secularization" by the anti-secularization camp.
Two things are going on at once: fewer and fewer people are involved in church, and what the churches actually preach is more and more this-worldly. 99 percent of what Joel Osteen preaches is about how to achieve worldly success, and Osteen is not the only one. Bruce's books is quite informative, and quietly amusing, on this emptying of truly Godly material from Christian preaching.
I strongly recommend that you read this book by leaving the first chapter till last. Begin at Chapter 2. This is because Chapter 1 lays out the abstract sociological theory while the rest of the books looks at the facts. I also happen to think that the hard, sober, observable fact of secularization is very well established, while some of the sociological theories appealed to by Bruce, concerning precisely why secularization occurs, are much more wobbly.