Because of Microsoft.
No, not because MS is failing to get corporations to adopt .NET (although that's got to be going slower than they expected) but because they are in their own gentle way distorting the market for .NET books.

Here's a reasonably original version of an exchange I recently had with a Manning author, Erik Brown.

MB: On a related question, Jack Herrington (the author of our
Code Generation in Action) suggests a reason why .NET books are selling poorly. He thinks its because of MSDN. I asked a couple of other people and they appear to agree. Bob Calco first told me that he certainly was buying .NET books (he hadn't seen our ADO.NET Programming even though he was interested in the subject). Then when I mentioned Jack's idea he suddenly turned around and agreed. He said the number of .NET books he had bought recently was low and that he was using MSDN a lot. He also uses all kinds of other sources for code samples, etc. There's a lot of useful stuff out there.

What do you think?

Erik Brown: Well, its an interesting thought (MSDN). They certainly churn out a lot of content, with sometimes daily updates on the various online sites such as www.windowsforms.net and www.asp.net. Add to these all the other free sites out there and you can typically find a how-to for most standard things you may wish to do. So I'm sure it impacts sales. So with companies no longer paying for most books, and consultants worried about the bottom line, the MSDN content is probably used more often than it ever was before.

Makes you wonder sometimes what future "books" will look like. The paper book is one dimensional sometimes. You could imagine my book, for example, as an electronic medium with a more streamlined and/or interactive tutorial and links to reference material both book specific and available online. Will be interesting to see what evolves.

(Erik is the author of Manning's Windows Forms Programming in C# )

MB: On the future of books, I'm not sure MSDN is a good indicator. My point is simply that MS is spending a lot on that facility and that in general that isn't the case--companies have real competition and cannot afford to spend real dollars on the information side, specially when there's a whole industry (book publishing industry) willing to do it. So, maybe the situation isn't as bleak as this makes it seem.

BTW I do not mean to say that books per se will not evolve. The electronic medium is so much better from many points of view. Unfortunately, reading from a screen isn't what people like. They want to recline, slouch, or simply angle their heads... :) When we can let them do that and make it electronic, then a new world of publishing will open up--I hope I'm still active then. Would love to be involved in discovering new ways to publish.

MB: Oh, and Bob Calco later added this:

Bob Calco: Since our conversation, I did a little more looking around here and
there is another issue---most of the .NET books we do have (including
subjects like ADO) are almost all from Microsoft Press. Turns out we
have quite a few--and most of them were borrowed out of my library to
various colleagues, hence my shock when you pointed out Jack's point and
I didn't see a slew of .NET books on my bookshelves. Erik's C# book and
a Prentice Hall book on .NET/COM interoperability are the only two
exceptions to MS Press here at the office. Thus I'd suggest that both
MSDN and MS Press are making it hard for other publishers to sell their
.NET books.

Final thoughts: For a few years now we have been staying away from .NET books--how many loosing business projects can a small company take on? And how many can I take--I hate to help good authors produce good content and then get miserable results.

Of course, MS Press itself is losing (or was losing) big money on their .NET books so the problem is not just MSDN and MS Press. The problem is also the slow penetration of .NET coupled with the "incredible, precipitous drop in the computer book market" (see Feb 19). But the market distortion they are causing may ultimately not be good for MS either.