You Probably Read Wrong and It's not Your Fault
I used to think reading was a chore. Like taking your vitamins, I thought it was something "good for you" that you just had to suffer through for hours at a time for some ephemeral benefits no one can quite pinpoint. Anytime I read a book, I read every single word, cover to cover. If I missed so much as a sentence, I reasoned, then I could not honestly say I read the book and conferred its benefits. Furthermore, I believed that once I read a book I'd absorbed its essence and thus had no reason to ever pick it up again.
Then I read Mortimer J Adler's How to Read a Book and it transformed my relationship with books. Since reading it, I feel as though my reading of every subsequent book has been forever improved. In large part, this is because Adler helped me to dispense with bad reading habits I carried with me, ones we're all exposed to in school. Freeing myself of some of the norms around reading, particularly reading nonfiction, helped me to enjoy reading more.
Needless to say, I recommend reading How to Read a Book yourself. I promise you'll gain more from everything you read, from fiction to nonfiction, novels and epics to news articles and fluff pieces, Greek tragedies and epics to song lyrics and online recipes. If you're curious, here are a few of the new habits I've picked up which make reading much more enjoyable and enriching.
Read Books You'll Read Again
To some degree this is just personal preference, but I stand by it as a general principle. There are a lot of books out there. Too many books. More books than you could spend multiple lifetimes reading. Most of those books aren't worth your time reading. Some are worth skimming, and a select few are worth reading closely. The specific books are different for everyone. Find them your select few, and read them many times over. Know them well, and you'll be both satisfied and enriched.
Reading All the Words
So you gotta read every word? Why? Is every word worth your time? Probably not. Read some of the words. Skip others. Skip sentences, whole paragraphs if you want. Sometimes you want to move fast and you've got the gist of what the paragraph will say after you've read the intro. If you're in a rush, move on. Move quick. If you must decide between reading 5 pages closely or 50 pages quick, pick the latter. You can always come back to read it again later.
Read out of Order
So you picked up a book. The back cover entices you, so you open it up. Naturally, your eyes go to the table of contents first. You see a heading that really catches your eye... but it's 150 pages in. The thought of going through that many pages to read a part you really want sounds like a slog. Then... just skip to that part. Read a few sentences, or a few paragraphs, or the whole darn thing. Read the first paragraph, then the fifth, then the third, then the last. When you realize you're confused about a particular part, go back to the table of contents and find the chapter that's most likely to clarify your point of confusion. Start the cycle over again.
When it comes to reading, why not skip straight to dessert? I mean, you don't even know if you want to read the whole book. Your time is valuable, and you have a right to be picky. You don't owe it to the author to read every word they wrote in order.
In the same vein, don't feel compelled to finish a book. Read it to your heart's content, then put it down and move on. If it's worth your time, you'll naturally gravitate back towards it. The only reason you should be reading a book against your will is because a grade depends on it.
Write in Your Book
Obviously, this rule doesn't apply if your book belongs to a library or anyone besides yourself. Assuming you own the thing though... write in it! "Sacrilege!" you say, "Books should be kept pure and clean." If your book happens to be a first edition of Canterbury Tales from a millenium ago, then yes by all means perserve its purity. Your $20 paperback that you got off Amazon? Don't worry, you were never going to resell it anyways. It's yours for good. Write in it.
Have a conversation with the author. You'll have a better time, and you'll gain more from the text. Underline parts that resonate. Write notes in the margins. Call out parts you especially agree or disagree with. Express your emotional response to the text. If the passage reminds you of something, make mention of it.
Conclusion
If it's true that (1) your time is valuable to you and (2) there are an incredibly small portion of books worth your time, then it stands to reason that you should be picky with what you read. What's the benefit in reading a book the "right" way just to cross its name off a list if you ultimately gained little value from it?
This isn't saying you shouldn't read books all the way through, or that you shouldn't read closely. Quite the opposite. You skim many books fast and sloppily so you can identify the books that are worth a deeper look. It's those books that you read slowly, in order and all the way through, taking time to ponder as you go.