Reading digest could be harder than reading the book itself, for analysis. When a 1000 pages book is reduced to 10 or 20 pages, we need to ask ourselves what had been left out. And this couldn't be done with objectivity. The author who wrote the digest surely choosed what to keep and to throw away according to his/her experiences. We also lose [The Why](The%20Why.md) of a book for the What and How by resting on the digest only. That's why we better read the with much selectivity (see: [Selective reading](Selective%20reading.md)) than reading its digest.