I'm halfway through this new book by Joshua Angrist and Jorn-Steffen Pischke and thoroughly appreciating it. I was planning to post when I'd finished but just found this very useful comment by Andrew Gelman, who has saved me the job.
http://www.stat.columbia.edu/%7Ecook/movabletype/archives/2009/02/mostly-harmless.html

Steven Durlauf, one of the editors of the New Palgrave Dictionary of Economics, was kind enough to talk to me about this massive and impressive project. The 2008 edition (being updated though 2009 as well) has some 7,500 pages in the $2950/£1710 print edition, containing 1,872 articles or about six million words. The Dictionary is an update of the 1987 1st edition, itself a successor to R. H. Inglis Palgrave's original Dictionary of Political Economy (1894–9), and Henry Higgs's revised edition, Palgrave's Dictionary of Political Economy (1923–6). The spirit of the Dictionary is an overview of the whole of economic thought, and as Professor Durlauf explained, the task he and his co-editor Larry Blume faced was to retain the best of the earlier edition but at the same time identify how economics had evolved in a quarter of a century, in order to commission new articles and remove many older ones. This involved a lot of reading – as he said: “It was my last chance to go to grad school.” I'm sure the two of them had to be extremely widely read to even embark on a project like this, and clearly are even more so now.
They identified about 15 entirely new areas in economics, such as behavioural economics. And, like any discipline, there are some fashions as well. No doubt the rational expectations sections written in the mid-1980s look dated now. The task took the co-editors a day a week on average and they spend five years preparing the Dictionary. One of the features I like about the Dictionary (its website is http://www.dictionaryofeconomics.com/dictionary) is that it retains some classic 1987 articles and has commissioned alongside them some new ones on the same subject. Prof Durlauf gives as a good example Amartya Sen's original article on justice, and a survey article on new perspectives by Bertil Tungodden; or James Heckman writing an update on his own earlier article. Showing the evolution of approach that you get from successive survey articles is a great idea.
The Dictionary is clearly a mainly online resource at present although later there will be single volume paperback companions which collect articles on specific themes. So this is the reverse of the Princeton University Press strategy of moving from the physical volume to the online world later, which I wrote about a few days ago. Prof Durlauf says he hopes it will be a tool for graduate students or scholars to start researching and identifying issues. The online format means it should be very easy to integrate into teaching and very accessible for researchers. It looks a terrific resource to me, especially because of the quality of the contributor list, and the sample articles I've seen have (unsurprisingly) been excellent. My quibble is that it's aimed too much at the academic market and library subscriptions. Non-academic researchers working in consultancy firms (like me) or public policy economists might also benefit from this kind of tool, but you have to email the publisher to get a price quote. This is probably a good way to maximise producer surplus given a fixed demand curve but not a good way to grow the market, it strikes me. I wonder if there isn't scope to experiment with pricing strategies for the wider community of economists, given that the marginal cost of supplying them is next to zero?