We have had issues with crafting appropriate reading assignments in our dense medical curriculum.  I am not sure how transferable these concepts may be to other fields, but we have found that clear alignment of reading to the session learning objectives is an important and necessary start. Faculty can sometimes include, for instance, an entire chapter because it contains the necessary prior knowledge but is not limited to that knowledge. Another successful strategy we increasingly use is a study guide to the reading. The truth is, outside of reading for pleasure or general knowledge, very few of us  read without a question to answer. Study guides provide those questions. They are particularly useful when it is more difficult to craft learning objectives specific enough to guide reading, and your learners are not skilled at seeing the forest for the trees. Some may argue that this is spoon-feeding – it can be done at that level (lots of details but no concepts). But if questions are really about new concepts for the student, I think it's simply a valuable aid to learning.