Upside of Irrationality is a mostly successful attempt to transform the scientific critique of the "rational consumer" principal into practical advice for living a better life. "Mostly successful" only because some of our habitual irrationality is fundamentally insurmountable -- there's almost nothing we can do to mitigate it.
But even when Ariely fails to deliver easy-to-follow advice for improving our lives, he still does deliver the same thought-provoking, fascinating experimental evidence for irrationality itself. For example, the sections on online dating (the return on your investment in an online dating service is so poor that you might as well not bother) and charitable giving (it's nearly impossible to feel the visceral sympathy for a million sufferers in some terrible genocide that you feel for a man choking to death at the next table) are both engrossing and well-written, but the advice that Ariely gives on both amounts to, "Be aware that you're apt to make a bad decision in these situations."
On the other hand, there are sections in which the science of irrationality is readily converted into practical techniques for living better, and these really shine. My favorite is the section on adaptation, that is, the way in which both terrible pain and incredible delights fade down to a kind of baseline normal over time. Ariely points out that adaptation can be slowed or even prevented through intermittent exposure to the underlying stimulus -- that is, if you take a break, the emotional sensation comes back with nearly full force.
Here's where our intuitive response is really wrong: we have a tendency to indulge our pleasures without respite, and to take frequent breaks from those things that make us miserable. This is exactly backwards. If you want to maximize your pleasure -- a great dessert, the delight of furnishing your first real apartment after graduation, a wonderful new relationship -- you should trickle it into your life, with frequent breaks for your adaptive response to diminish. If you want to minimize your pain -- an unpleasant chore, an awful trip -- you should continue straight through without a break, because every time you stop, your adaptive response resets and you experience the discomfort anew.
Also outstanding is the section on motivation in the workplace, and the way in which imbuing work-tasks with even a little meaning can make them much easier to complete and much more satisfying. There are several pieces of good, practical information here, all couched in Ariely's breezy, easy to read style. Even if Ariely's research doesn't always neatly translate into simple heuristics, he's such an interesting writer and thinker that I'll read anything he writes.