To that end, I strongly recommend Michael Porter, who literally wrote the book on modern "Competitive Strategy". There is no other single source of strategic theory that is better than this. Anybody that has taken a b-school class on strategy worth their tuition will recall concepts like Porter's 5-forces.
Other answers seem to offer more recently offered books and some might dare to argue his frameworks are dated but really it's in a robust, tried-and-true-kind of way. Other books that try to cover defining strategy, value chain, industry analysis are often derivative of his work.
If you don't end up reading it at least get a list of his key concepts and google the shit out of them. They all seem like a "duh, i knew that" on paper, but you should have these theories in your back pocket whenever you need to formulate a battleplan.
http://en.wikipedia.org/wiki/Porter_generic_strategies
http://www.amazon.com/Competitive-Strategy-Techniques-Indust...
The book Outhink The Competition[1] really inspired me to start down this path. There's some good stuff in there, and that led to me finally picking up my copy of Porter's Competitive Strategy[2] and digging in. I take this seriously enough now, that I wrote a quick and dirty internal app just for managing competitive intelligence and keeping track of documents and links related to competitive analysis and strategy formulation.
Which, when you think about it, is a Good Thing. I mean, if you're talking to an investor and they say "how do you intend to compete with $FOO?" It's probably good to have a solid understanding of exactly how you intend to do that, instead of just saying "Oh, we'll out execute them." Especially when you choose to play in crowded markets like we do[3]...
[1]: http://www.amazon.com/Outthink-Competition-Generation-Strate...
[2]: http://www.amazon.com/Competitive-Strategy-Techniques-Indust...
- Are the customers genuinely frustrated with the low quality of the products currently on the market? How do you know? How can you convince them you're better?
- Will you create new markets? If not, can you differentiate yourself enough that you're not competing purely on costs? Can you beat your competitors on costs? How long can you sustain that? (i.e. as your costs rise can you stay competitive)
The typical books here are:
http://www.amazon.com/Competitive-Strategy-Techniques-Indust...
...about competing in markets, and...
http://www.amazon.com/Blue-Ocean-Strategy-Uncontested-Compet...
...on creating new markets. (At this point I've only read the latter. The other one is on my queue. :-) )
I'd suggest some general "business strategy" works that will help you understand the context of how/why the very highest level business decisions are made, as well as some works that deal with tying together strategy and tactical execution (which includes technical initiatives).
1. Understanding Michael Porter - John Magretta. http://www.amazon.com/Understanding-Michael-Porter-Essential...
Porter's framework is VERY influential in the business world, and having at least a passing familiarity with his work is important at the higher levels. Going straight to the primary sources (Porter's books) can be a bit daunting as they are big, dry, and academic and not exactly what you'd call "page turners". This book is a fairly solid overview of the key elements of Porter's approach, and a good read before diving into the meat of Porter's works.
2. Competitive Strategy - Michael Porter. http://www.amazon.com/Competitive-Strategy-Techniques-Indust...
3. Competitive Advantage - Michael Porter. http://www.amazon.com/Competitive-Advantage-Creating-Sustain...
4. On Competition - Michael Porter. http://www.amazon.com/On-Competition-Updated-Expanded-Editio...
5. Good Strategy, Bad Strategy - Richard Rumelt. http://www.amazon.com/Good-Strategy-Bad-Difference-Matters/d...
6. Blue Ocean Strategy - W. Chan Kim, Renee Mauborgne. http://www.amazon.com/Blue-Ocean-Strategy-Uncontested-Compet... This book has its critics, but I think it's a worthwhile read. Some people argue against the whole idea of a "blu e ocean" market, but even if the authors aren't 100% right about everything, I think the lines of thinking this book fosters are valuable in a general sense.
7. The Discipline of Market Leaders. http://www.amazon.com/Discipline-Market-Leaders-Customers-Do... I think very highly of this book and the author's approach to strategy. It's not radically different from the Porterian approach in some ways, but I'd say it's narrower in focus and simpler. The big takeway is the idea (which should be obvious, but often isn't) that "you can't be everything to everyone". The authors push a model of choosing a market discipline to appeal to a certain type of customer, and making that discipline the core of your business.
8. The Machine That Changed The World. http://www.amazon.com/Machine-That-Changed-World-Revolutioni... Have you ever wondered what this "lean" stuff is all about? Or why Toyota is so revered by business leaders? Here's a good place to find the answer to those questions.
9. Working Knowledge- Davenport and Prusak. http://www.amazon.com/Working-Knowledge-Thomas-H-Davenport/d... Perhaps the seminal book on Knowledge Management, or at least one of them. If you want to understand the importance of knowledge in an organization, this is a very valuable read.
10. Outside Innovation - Patricia Seybold. http://www.amazon.com/Outside-Innovation-Customers-Co-Design...
11. The Future of Competition. http://www.amazon.com/Future-Competition-Co-Creating-Unique-...
12. The Balanced Scorecard. http://www.amazon.com/Balanced-Scorecard-Translating-Strateg...
13. Strategy Maps. http://www.amazon.com/Strategy-Maps-Converting-Intangible-Ta...
14. The Strategy Focused Organization. http://www.amazon.com/Strategy-Focused-Organization-Scorecar...
15. If Only We Knew What We Know. http://www.amazon.com/Only-Knew-What-Know-Knowledge/dp/14516... Another seminal title in the Knowledge Management world.
16. Common Knowledge - Nancy Dixon. http://www.amazon.com/Common-Knowledge-Companies-Thrive-Shar... Another seminal title in the Knowledge Management world.
17. Winning The Knowledge Transfer Race. http://www.amazon.com/Winning-Knowledge-Transfer-Michael-Eng...