Ideas worth remembering are difficult to ignore. These sticky ideas will haunt you until you pay them sufficient attention.
Reading is a popular means of discovering new ideas. We read books hoping to be stopped in our tracks by ideas with potential to change the way we think.
Certainly these 'aha' moments are an exciting part of reading, but I've grown to favor sticky ideas over moments of epiphany.
Sticky ideas aren't immediately identified as valuable. It's never love at first sight with sticky ideas. It's more of a slow burn. Days will pass from your initial encounter before you realize a sticky idea has been pacing in the back of your mind, gently pulling on your sleeve for recognition.
A book may not invoke any 'aha' moments, but usually, if you're reading a decent book, there should be a sticky idea to chew on. If your mind doesn't wander to an idea surfaced by the book you're reading, it's probably not the right book for you.
You don't need to chase sticky ideas. They will come to you.