For some time I've posited to colleagues that a good way to gauge the job market for a given technology is to go down to PowellsBooks (or its equal in your hometown) and measure and compare the shelf space given over to different technologies and languages every couple of months. A related indicator is how likely you will be able to sell back your used books.

I had the experience today that I couldn't sell back about four Java books at either of the two PowellsBooks locations. The Java shelf space at Powells, has shrunk dramtically over the last six months, and I've noticed new titles are not being published at the rate they once were. The CeeSharp section, however, keeps growing. C++ shelf space has become pitiously small. (For the record, I work in JavaLanguage.) I know for a fact that Java jobs are far, far fewer in Portland than they were a year ago. I'm not sure if there are more C# jobs.

Do you think the publishing market and book sellers know before we do (or at least before we will admit to ourselves as programmers) what is going on with technological trends? Publishers are just about sales. It doesn't matter to them which technologies are hot. I don't hear many JavaLanguage programmers saying they are switching to C#, but will they? If my theory is correct, they (and C++ people) must be doing it already. Either that or the total job market for Java has shrunk while C# has grown, which could be true because of the dot com bust. Thoughts?
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My guess is that there's some sort of co-efficient concerning the maturity of a given technology. With a new technology like DotNet, publishers rush in to provide explanation for those who need to get up to speed quickly on the technology. In the initial stages, at least, most of those grabbing up the books were probably already working with prior Microsoft technologies.

''I would hope that some of this is the customer base for a language growing in discernment. Certainly for C++ there just aren't that many books out there worth buying. BjarneStroustrup, AndrewKoenig, ScottMeyers, books in the C++ in Depth Series, less than a dozen others as far as I know. If the other books are disappearing, then good riddance. They mostly weren't worth buying anyway.''

There's always been a big publishing industry for VB, Com, WFC, and other such things that are -- to varying degrees -- subsumed or denigrated by DotNet. The publishers of those books sent their armies of authors off produce new titles for the new technology. (Unfortunately, many of the early titles belong in a trash bin rather than on a used books shelf.) 

At the very least, DotNet has been very good for the employment of writers. But I suspect that it's still too early to know if the deluge of titles indicates much about the actual adoption rate of the new technology.

(I'd also suggest that other places might have a pale imitation, but I doubt that anyplace else is fortunate enough to have a "hometown equivalent" of PowellsBooks.)
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The books section of the Chicago MicroCenter is the largest computer book section I've ever seen and I've seen the following: 
	* Tremendous increase in CeeSharp books, but at the expense of VisualBasic and C++. 
	* The Linux-Unix-MacOs aisle has remained the same size, but the shelf space of Mac books is growing (the Linux shelf space is shrinking a bit, and/or combining with other Unix books.
	* A dramatic increase in Oracle books. This seems to be at the expense of MicrosoftAccess books and (for some strange reason) 'little languages' like Scheme, Haskell, Squeak and arcana like Fortran and Cobol (or maybe they've just been moved somewhere else).
	* The makeup of the clearance aisles still seem to be old java books, a raft of stuff from the 1990s that never sold (and never will), and (best of all) O'Reilly overstocks of books that have a new edition out. 

So, from the looks of things in Chicago: MacOsx, Oracle, and CeeSharp are the big winners. 

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The local Waldenbooks has shrunk their once-large Computer section to a single vertical shelf unit, consisting entirely of ''... For Dummies'' books and a few Cisco certification guides.  No Java, no C#, no VB, and no C++.  Waldenbooks has never a great place to buy computer books, but they have apparently given up.

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I'd say it's more of a measure of change or trends than a measure of existing jobs. 

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It's 2014 -- How about an update, it's been a dozen years since the last edit of this page - at the same store, but this time maybe include measurements in inches or feet and inches?

''Do book-stores still exist? :-) Maybe Amazon.com Page-Down button pushes can be used instead of shelf width.''