If you want a serious suggestion from someone who made it up the consulting ladder some years ago, is now making 50% more cash for 30% less hours (yes - the nirvana of well networked, reliable-income freelancing - and no, not contracting, before there are any wise cracks!) and still reads both old and classic publications…..
For a quick and easy way to keep up to date with social affairs I recommend The Week - don't laugh, your clients may actually prefer to have intelligent people who know something of the world, rather than just a functional droid.
For negotiation - by far the least developed skill of most consultants today (so much so I'm thinking of running classes in my alcohol drinking time) then Fisher & Ury's "Getting to Yes" is very useful - but it does require that you practice the skills all the time; negotiation is not well suited to purely book based learning.
For strategy and cutting through the bull, then you should speed-read Michael Porter - his early work is still spot on for a simple reminder that there only are a limited number of generic strategies. If your client (or your own start-up pet project) don't conform to his breakdown then they/your are 99% probably going to fail OR 1% doing something so brilliant even Porter didn't see it coming - you decide which is more likely. Don't however read all of it - each page of brilliance is padded by eighty pages either side.
For becoming rich and understanding personal success, read Felix Dennis (his autobiography), quite simply the only "How to get Rich" book worth bothering about. Not because it tells you any secrets (there are none), but because he will force you to confront yourself in a completely honest way. As a successful poet (in addition to multi-billionaire), he is also an extremely good writer - some of his more personal prose moments have a brutal human truth I had not read since first reading Hemmingway.
And speaking of which, read Hemmingway (For Whom the Bell Tolls/The Old Man & The Sea) to understand the human spirit, Scott Fitzgerald (The Great Gatsby) to understand the pursuit of money, happiness and the American (now global) dream, and any of Le Carre's Cold War novels to remind yourself how quickly our world can change, and yet stay the same.
And if you are recently unemployed, read Jeffrey Archer (any old drivel will do) to remind yourself that as long as you have the guts and determination you can overcome even bankruptcy and a complete lack of talent to become a millionaire without having any discernable talent whatsoever.
I hope you enjoy them, learn from them and find some time to enjoy your life.