"Now, Discover Your Strengths" by Marcus Buckingham and Donald O. Clifton is the book I have most frequently recommended at work. For about ten years now, I have successfully encouraged the majority of my direct reports to read it and take the strengths assessment, and in the cases where they themselves are managers, many have adopted the book for their own teams as well. When I am asked to mentor less experienced colleagues, I usually start with this book.
Marcus Buckingham also co-authored "First, Break All The Rules", and two books are natural companions of each other. "First, Break All The Rules" asserts that the best managers focus on their employees strengths, and find ways for employees to make more use of their strengths in their everyday work, giving them the confidence to so, and helping them develop their strengths and themselves accordingly. "Now, Discover Your Strengths" tackles the very important step of identifying what those strengths are, and offers some advice on managing people based on their strengths.
I find the book valuable in several ways. For example, many people, until they take a deliberate review of their strengths and core values, don't have a clear idea of what their strengths are or how to articulate them. While it is clear they know when certain styles or types of work feel satisfying and when they are performing well, often the underlying reasons go unexplored.
Further, the "conventional wisdom" as it relates to employee development, as discussed in "First, Break All The Rules", tends to focus on employee weaknesses. This can be seen in many performance review templates, for example. I have seen how this negatively employee confidence, which can have a very significant impact on performance. In contrast, I have used the strengths assessment to structure a highly productive conversation with individuals that puts the emphasis on their strengths and core values. This provides a framework for us to discuss how their strengths can be used more frequently.
One of the most satisfying results in recommending this book is seeing the positive impact it has on the reader (when integrated follow-on conversation, of course). I believe the positivity comes from a number of angles:
The act of sharing the book and having follow-on conversations is appreciated by the employee in the manager actively taking an interest in them as a person. It helps both the employee and manager have a conversation about the employee in a safe, work-related environment.
The underlying theme of focusing on strengths is a positive topic. In follow-on discussions, the manager has the opportunity to recall the employee's good work and relate it to their strengths.
Because people, by definition, care about their strengths and core values, it is easier to channel this interest into employee development activity.
For both the manager and the employee, the book serves as a great reminder that the focus of performance should be on the outcome, not the work style. This is particularly relevant in cases where managers get caught up in managing to "their way" of doing things (which may not suit the employee), and employees correspondingly lack the confidence to get things done in ways that are most comfortable (and more productive) for them.
While there are many tools and books that will bring to light an individual’s strengths, preferred styles and core values, I have little hesitation recommending "Now, Discover Your Strengths". I find it is broadly accessible, gets the job done, and presents a fine framework for engaging and productive conversations between the manager and employee.