Many people aren't learning but feeding their biases. Not strengthening in new information but being stronger in their original stances (Seeking the known unknown and not the unknown unknown as Freud stated). This has always been my challenge to people. Is your end goal rooted in confirmation bias or gaining new information?
Entertainment is the primary driving force for many. Even when it comes to the activity of reading many are solely seeking books and highlighting information that supports ideologies they already believe. To grow one must seek counter information along with and then trace the scientific origin and connections of such information.
Self-help books are some of the worse books to read for personal growth. And I say that referencing books with little to no scientific proof or references. Many are sharing their stories and ideologies with no credibility in their works outside of personal experiences. The subjective sentiments are too narrow to genuinely help. Instead, one should be given words, theories, and definitions to be able to overstand the why, how, and process of something to determine what truly works for them.
I see many avid readers not growing because they only read what confirms innate or inherited ideologies. I.E a religious person solely reading the book of their faith. Although you may be growing stronger in your ability to recall and recite stories and motivational quotes, they close themselves off to growth of knowledge and the more applicable approaches. Applicable as in modern, physical, and physiologically applications. Doing so allows them to strengthen in their application of their book along with argument and truly entice the development sought.
A book is no better than compared forms of resources if a person continues to read the same information in different wording. One should seek to know definitions and theories and not rely on where society points a finger too. Because the common societal mind is one for entertainment and self-satisfaction over development. More commonly a person accepts recommendations coming from list that aren't filled with the most educated but have become most popular by marketing and successful mouth to mouth promotion.
If a person is truly seeking to learn for growth they must learn the science of the mind and if seeking deeper, the brain. Psychology, sociology, and neurology hold the true sources of information for personal development. Learning the consilience of the three is the true way for an individual to develop.