Everything can be considered fluff if you're familiar with the topic already. For example, I respect Richard Dawkins and agree with his position, but if you rea

Everything can be considered fluff if you're familiar with the topic already. For example, I respect Richard Dawkins and agree with his position, but if you read two or three of his books, everything else is just "fluff". Similarly, if you already know Calculus, every other book on Calculus will be just "fluff". So, this basically means that you need to be reading books on topics that you don't know. The main difference I would make here is not in terms of having fluff or not, but if the book is well written.