I think the difference between reading the whole thing and the summary is about making the knowledge yours. If the non-fiction book has merit, it usually inclu

I think the difference between reading the whole thing and the summary is about making the knowledge yours. If the non-fiction book has merit, it usually includes the rationale and real-world examples of the thing explained. Therefore you can examine the idea and have a deeper understanding of the subject or even improve on the original work. Summary forces you to memorize a few facts and you wouldn't even have a basis to evaluate the validity of the idea. I read summaries only when the book is written for the general public and I already have expert knowledge about the subject. In my opinion, reading summaries give a false sense of accomplishment. Reading is not about understanding one idea and implementing it. It is about understanding how to reach that idea, therefore you can improve on it.