I found Ordeal By Fire to be very engaging right away. I had no trouble getting into it. However, that might be due to the fact that I very rarely ever have trouble getting into a book and also consider the Civil War to be one of my favorite time periods in history. Regardless, it did grab me from the start.
I agree with the authors on two main points. First, I believe that the political machinations (both North and South) in the decades leading up to 1861 had more to do with making a civil war an inevitable conclusion, then most historians for the past 150 have given them credit for. Both sides, were heavily influenced by extremists:
1) In the North by the abolitionist / anti-slavery movement which insisted on seeing the cause in overly religious tones and viewed those who practiced slavery as wallowing in sin and evil (thoughts which do not lend themselves to polite discourse and compromise) had several good leaders, among them William Lloyd Garrison.
2) The pro-slavery movement, which viewed slavery as initially a "necessary evil" and later made the radical shift to considering it a "positive good". They came to view any attacks on slavery as simultaneous attacks on the South, the Southern way of life, and on them personally. John C. Calhoun was one of the more influential and vocal proponent of this position.
Ultimately, in both these extremes, these groups took the situation way to personally. And there-in lay the problem. In addition, the vast majority of the population, North and South, was NOT represented by either of these extreme positions; their thoughts on the matters of slavery and the opposing region were consistently in the middle somewhere. Just as their were Northerners who favored leaving slavery alone, there were also Southerners who were unhappy with the institution. The situation was NEVER so cut and dry as the extremists wanted people to think it was (a situation as true today as it was then).
The second point of the authors that I agree with, is their emphasis on the how the changes in both the world and the US' economy affected the North and the South, but in different ways. I have always thought that economics did more to cause the Civil War than either slavery or regional disagreements. During the time of Industrial Revolution, the North took full advantage of the new technology available and thus the US took their first steps towards become a worldwide economic powerhouse.
Unfortunately, the South chose to wallow in the past and was thus unable to break their collective dependence on slavery. They really needed an intervention! However, the way that the South had structured their economy made it pretty much impossible for them to end slavery on their own, it truly needed slavery to work. Also, slavery was an investment; a plantation owner could make more money per year by investing in the buying, breeding and selling of slaves, then in other pursuits. If something makes you money......Then what is the incentive to stop doing it?
The economic pressure, exerted on the South by the North, to modernize, I feel made the Southerns that much more resistant to change and that much more determined that "slavery" was both a "good" in this world and a "necessary" fact of nature. In short, slavery went from a "necessary evil" to a "necessary good", thanks to economic concerns.