We all receive email -almost on a daily basis- from fellow marketers wishing to sell their e-books.

Now, there is absolutely nothing wrong with that, aside from the fact that the information in these e-books might be outdated. Software and hardware technologies change at such a high speed it's incredible. You read something now and in 3 hours something new comes up.
If you don't believe me go over to SlashDot or PCMagazine or Extremetech or TechCrunch or TheRegister and click on the refresh button of your browser every 3 hours and you'll see exactly what I mean.