This might be true if you use sparknotes as a 100% substitute for reading, but I disagree if you're using it as a tool to better optimize how you read. One of t

This might be true if you use sparknotes as a 100% substitute for reading, but I disagree if you're using it as a tool to better optimize how you read. One of the biggest parts of learning is just knowing where you need to go to get the information. The summary won't tell you everything of value within a book, but it should be sufficient to guess what sort of value is in the book, and specific chapters within. For example if you can figure out that 25 out of 30 chapters of a book either are either rehashing things you already know or are irrelevant to what you are trying to learn, then you can focus your limited time on the remainder where you have better odds of finding what you are looking for. Of course you can kind of do this just by looking at a table of contents, but sometimes it can be quite difficult to determine from the title alone what a chapter will contain and the level at which it will be discussed. Further, it's great when you're going back to something you've already read to know where to look for some specific piece of information because the goal is not to memorize data but to understand broader concepts. A summary also serves well as a 20,000ft overview of a topic that gives you the breadth before you dive into the depths of the parts that are more useful. You can pick up context that might be locally helpful but not really something you want to spend a great deal of time on, you can have some idea of what you are going to learn from what you do focus on, and you can perform a sanity check on what you believe you already understand (ie if the summary doesn't make sense, you probably don't know it as well as you might have thought). Of course the only way to guarantee you don't miss anything at all is to read through everything 100%, but generally what you are looking for is not going to be hidden in a throwaway line in an otherwise unrelated section. Very often the gist is all that really matters.