I've seen many glowing references to Feynman's Lectures on Physics, but this is the first time I've seen them called a failure. Could you share a bit more about why they're considered a failure?
The lectures are well-regarded by many, but it's been argued that they're ineffective for teaching undergraduate students the process of solving physics problems.
Feynman himself was an exceptional mathematician, and used a very mathematical approach to solve problems. But once arriving at the solution, he identified a concise intuitive explanation, which he then presented to others. Everyone was impressed with the brilliant intuition, but it didn't accurately reflect the more laborious and mechanical approach he used to solve the problems [1]. The Lectures of Physics are similar: a series intuitive explanations that would be difficult to discover independently without actually working through the math.
Problem with these lectures is, they require too much work for a layman to benefit from them; at the same time, they are too elementary to be useful for a seriously interested person (say, an engineer). The book may still be good for schoolchildren who are interested in physics. I find more traditional courses, such as Berkeley Physics Course, more informative.
Feynman himself was an exceptional mathematician, and used a very mathematical approach to solve problems. But once arriving at the solution, he identified a concise intuitive explanation, which he then presented to others. Everyone was impressed with the brilliant intuition, but it didn't accurately reflect the more laborious and mechanical approach he used to solve the problems [1]. The Lectures of Physics are similar: a series intuitive explanations that would be difficult to discover independently without actually working through the math.
[1] http://www.stephenwolfram.com/publications/short-talk-about-...