I am a huge fan of Peter Gill's work, and if you are looking for the best possible to reflect on intelligence as it is generally defined today (the province of governments and to a lesser extent the corporate world), this is both the most recent and the best book to get. I also recommend Mark Lowenthal's Intelligence: From Secrets to Policy, 5th Edition.
Use Look Inside feature above to get a feel for the book. Of all the books I have reviewed, this is the one that comes closest to my own concept for a book I am working on now, and I very much like the manner in which the authors have organized the work, to include their section on "Why Does Intelligence Fail," which happens to be what I have been focusing on since 1988.
Where the book fails, as do all books in this genre, is in not acknowledging that intelligence is decision support defined by its outputs, not its inputs. This is a book that is still state-centric, assumes secrecy is a dominant force, and that policy is the intended beneficiary. It does at least make a stab at acknowledging corporate intelligence, but see my list of recommended readings below. More properly understood, decision-support is a craft that can be applied by all eight "tribes" of intelligence (academic, civil society, government, law enforcement, media, military, and non-governmental/non-profit), and our greatest challenge today is the need to move beyond the government-secret-policy view of intelligence, and instead advance toward M4IS2 (see the graphic above with the book cover), Multinational, Multiagency, Multidisciplinary, Multidomain Information-Sharing and Sense-Making.
As much as I admire the authors and the book, I really do wish all authors would read more broadly and include a more diverse collection of perspectives. My own master list of books I have reviewed on intelligence (as of a year ago, over 300 books) can be found by searching for the following, with all reviews leading back to their Amazon pages:
Worth a Look: Book Reviews on Intelligence (Most)
Here are nine other books I recommend.
Strategic Intelligence and Statecraft: Selected Essays (Brassey's Intelligence & National Security Library)
Very Special Intelligence
Intelligence and U.S. Foreign Policy: Iraq, 9/11, and Misguided Reform
The Art and Science of Business Intelligence Analysis (Advances in Applied Business Strategy)
Early Warning: Using Competitive Intelligence to Anticipate Market Shifts, Control Risk, and Create Powerful Strategies
Business Blindspots: Replacing Your Company's Entrenched and Outdated Myths, Beliefs and Assumptions With the Realities of Today's Markets
Business and Competitive Analysis: Effective Application of New and Classic Methods (paperback)
The Extreme Searcher's Internet Handbook: A Guide for the Serious Searcher
I hope the above is understood to be a strong recommendation to buy and read. I was not happy with the absence of reviews and one light review. The craft of intelligence is well defined in the forthcoming Routledge Companion to Intelligence Studies that will be in my view the single most useful teaching book in the near term, along with this one.
Best wishes to all
INTELLIGENCE FOR EARTH: Clarity, Diversity, Integrity, & Sustainability