For a background on the field, I’d recommend reading Henry Mintzberg’s Strategy Safari. Dumb title, but a great book; I think that Mintzberg is one of the best academic theorists on corporate strategy today and all his books are worth reading. HBS publishes a little primer called On Corporate Strategy that is also useful, and the Economist has one of their pocket books on topic that has useful definitions and so forth. Two Economist writers (Mickelthwaite and I can’t remember the other) have written a scathing critique of the consulting industry around corporate strategy, entitled The Witchdoctors which is very entertaining and well written. (Less successful but more popular is their history of the idea of the firm, The Company which I found dull.)
The classics in the field, which everyone refers to but never reads, are about military strategy; they include the Prussian general Clausewitz On War, Liddell Hart Strategy and Sun Tzu The Art of War (the best translation is by a dear teacher of mine, Kidder Smith). I would recommend not reading any commentaries on these; they’re easy enough to read themselves, at least in translation, and the books about them generally suck. If you really want to get into the military side of things, the US Civil War is the interpretive lodestone; there’s a great atlas of Civil War battles that everyone refers to but the name of it escapes me at the moment.
Michael Porter’s corporate strategy books (Competitive Strategy and Competitive Advantage) are supposed to be the canon for corporate strategy, but they don’t do it for me. I always feel like he’s writing about a world that doesn’t exist any more and in contrast to say Peter Drucker (fabulously good), Porter seems dated and of little practical use. But many of his ideas have become so influential that they’re just in the air and so perhaps reading them in their original guise doesn’t have the same impact.
Wharton’s compendium on the topic (I think it’s Dynamic Competitive Strategy, or something like that) is good, serious and useful. Robert Grant has a practical book called Contemporary Strategy Analysis that I’d also recommend. I guess it’s a textbook, too.
I’ve found that van der Heijden’s Scenarios book is also very practical, surprisingly enough. van der Heijden is a part of a movement that emphasizes a formal approach to “scenarios” to think about the future and how to respond — he was in a Shell Oil planning group that famously predicted the oil shocks of the mid-seventies and helped Shell to respond quicker than their competitors. But his book has useful suggestions on how to run workshops to create scenarios. Peter Schwartz (who wrote the excellent Art of the Long View) is another proponent of this approach, which I like, but which I don’t hear about so much these days.
Game theory is another good approach, one with a large literature, albeit very abstract and focused on inter-firm interactions. If you’re interested (“if you’re game…”) you might start with McMillan’s accessible introduction, whose name escapes me at the moment.
Currently, I guess, people like Geoffrey Moore (Crossing the Chasm was the first of his trilogy) and Christensen who wrote Innovator’s Dilemma are widely cited, although they’re more focused on technology and start-ups.
You really need a solid understanding of managerial finance to make valid recommendations; any good textbook will give you the introduction (I like Brearly & Myers, Principles of Corporate Finance but that’s just a user’s bias) and then there’s the excellent Economics of Strategy that I highly recommend; it’s not easy going though. There is a lot of really terrible financial analysis today around technology investment and most “TCO studies” are worthless.