I have seen this phenomenon too - try finding a "hard" math or physics book at your local bookstore, or even a Martin Gardner-like problem book. I couldn't, I h

I have seen this phenomenon too - try finding a "hard" math or physics book at your local bookstore, or even a Martin Gardner-like problem book. I couldn't, I had to order them special. My personal feeling is that this is caused by the "edu-tainment" movement. It's fun to feel like you're learning. However, truly learning something is difficult, so publishers dumb it down enough where you can feel like you're truly learning, but removing all the hard work required for true understanding. The proof of the pudding is in the eating, and these sorts of books proved more popular than the harder non-fiction counter-parts, leading to the situation we have now.