Here’s a strategy I’ve found useful for learning dry and difficult material quickly. At various times, I’ve used it to build up my knowledge of subjects like economics, investing, writing and computer programming languages. Some people have been surprised at how fast I can learn these kinds of skills, but I think anyone can do it with the right plan. Of course, you can use this to teach yourself interesting things as well, but most people don’t have any problem learning stuff that’s fun.
Bombard yourself with information — Don’t try to slowly digest the material you’re trying to learn; immerse yourself in it. Read it quickly, so that you’re drowned by it.
Identify the key concepts and make them yours — Try to comprehend the Big Picture. Don’t worry about the details. Recognize the broad overview so that you can understand the fundamentals of the subject.
Only memorize what absolutely has to be memorized — Don’t fret over details that can be referenced later. Most subjects have specific facts that you must know. Learn them. But don’t worry about details that can be obtained through reference works when needed.
Get some feedback on your understanding — Find some sort of comprehensive practice exam and take it. You will probably do poorly, but from your results you’ll be able to tell what you learned and what slipped your mind. Try to correct your mistakes as soon as possible.
Bombard yourself with some more information, but from another source — This is the key step. Find some other source — not necessarily another textbook — and use it to glean as much information as possible. Maybe use multiple sources. Try to focus on your weak points after your first reading.
Get some real-world feedback — Find a community fluent in the knowledge you’ve tried to learn. See how well you fit in. For example, if you’ve tried to learn a language, see how well you can interact with others who speak the smae language.
I’ve never tried to acquire skills with this or any similar method, yet I recognize that it might be useful in certain circumstances. It doesn’t seem appropriate for a subject that you need to learn thoroughly — your college major, or something germane to your career — but it might be useful in situations where you’re trying to acquire secondary knowledge.