I personally find lecture notes superior to textbooks. Text authors frequently fail to edit their work down to the essentially material. When I am first learning a subject I want the key results. Once I understand the core ideas I can look up more details when I need them. Textbooks can be great for reference but as an introduction I like notes.
I am mostly familiar with studying math, economics and computer science. So I am not sure how my experience compares with people studying other subjects.
In line with my continuing self eduction...
What are the most important or personally influential academic papers you've ever read? Which ones are essential (or just good) for an informed person to have read?
Is there any body of research of which you found the original papers much more valuable than than the popularizations or secondary sources (Wikipedia articles, textbook write ups, ect.), for any reason? What was that reason? Does anyone have a good heuristic for when it is important to "go to the source" and when someone else's summation will do? I have theoretical preference for reading the original research, since if I need to evaluate an idea's merit, reading what others in that field read (instead of the simplified versions) seems like a good idea, but it has the downside of being harder and more time-consuming.
I have wondered if the only reason to bother with technical sounding papers that are hard to understand is that you have to read them (or pretend to read them) in order to cite them.