The Cambridge Handbook of Expertise and Expert Performance (CHEEP) was the state of the art in expertise research at the time of publication, and it remains a resource that I recommend and refer to frequently. Editor K. A. Ericsson, in my view, authored some of or simply the most important expertise acquisition research in the last century, overturning age-old beliefs about talent and innate ability, and he did a very admirable job of it, all things considered. Other contributors, such as B. J. Zimmerman, are authorities in their own right within their fields.
What the book is
Importantly, CHEEP is an academic resource on expertise acquisition for domains that have been researched, not a guide to becoming an expert. If your questions revolve around appropriate theoretical frameworks for expertise, how to measure expertise, domains of expertise and the mechanisms which underpin expertise, then this book is an invaluable introduction and reference. If you are looking for a resource on becoming an expert yourself, then your mileage may vary much more, depending on your level of education in academic psychology.
With that said, cognitive science moves quickly, and I would say that while the book's contents remain relevant, some/many of its topics are already understood in greater detail than they were in 2006. There are a number of developments I would like to see included in a hypothetical update, such as retrieval-induced forgetting/facilitation, the growing embodied cognition literature and, perhaps more regrettably, a lot of recent skills acquisition research.
Despite the increasingly worn pages of my copy, occasional missing recent development, and other signs of aging, the Cambridge Handbook of Expertise and Expert Performance nevertheless earns itself a 9/10 and a prominent spot on my shelf. It is an unrivaled introductory text to the field of expertise research.