As far as I know, this isn't a Christian book. It's a book by two people who have done a lot of research (with Gallup) into people's working patterns. But we can learn from them, and it's always nice to see secular researchers getting back to where the Bible said they should be, which they kind-of do...
The basic thesis of the book is that we work best by focusing on our strengths rather than our weaknesses. I think that's a good point, and they justify it well.
The book is based around the question "At work, do you have the opportunity to do what you do best very day?" They asked that to a lot of employees, managers, and so on, and found that the people who said "yes" were more productive, enjoyed work more, were healthier and happier, and so on. They found that companies that enabled employees to do that worked better as a whole.
The authors then go on to identify 34 different "strengths", which is enough for there to be 34C5 = 278,256 different combinations of top 5 strengths, even if you ignore the order. Including ordering too, that's over 33 million permutations. And they offer an online test to determine what your top 5 are. There are then a good number of suggestions of how to use your strengths to deal with weaknesses, how to encourage others to use their strengths and so on. A lot of it is common sense, but common sense isn't always very common, as evidenced by some in the Church of England who think that all clergy should be able to do any clergy job.
Weaknesses in the book - they don't explain exactly where the 34 strengths come from. I very much doubt that they are all independent. For example, I would expect people who score highly on "intellection" also to score highly on "deliberative". Nor do they explain why 5 is the magic number - I would expect that some people are more focused than others - one person might have 80% of their abilities on one skill, another might have 20% distributed across each of 5 skills. And some people might just have more innate ability than others anyway. Some of their suggestions are just plain silly too - replacing interviews with just competency measures, for example - often basic conversational skills and personality are important, and you miss that through just doing tests.
There are some good insights as well - for example the way that performance reviews often don't measure performance in the ways that matter. All in all, I found it a thought-provoking read. I don't agree with everything in it, and some bits were overly long and tedious, and the good research doesn't justify all the conclusions they hang on it in terms of the 34 types. But in terms of thinking about what it means for us to be given different gifts, and for us to be different parts of the body, and to be supporting one another as different parts of the body, it was well worth a read.