All successful investors read a lot. It's a common denominator you'll find among most smart people. Charlie Munger once said, "In my whole life, I have known no wise people who didn't read all the time – none, zero."

But all good ideas can be taken too far. Reading is one of them. 

Reading is powerful because it opens your mind up to new ideas you hadn't thought of before. We're all a little malleable in that way. But this can be equally dangerous if you're reading nonsense, bull, drivel, gossip, or other stuff that opens your mind up in ways you'll eventually regret. There's an important difference between "reading lots of stuff from a variety of fields" and "reading every word in front of my eyes." 

Every reader needs a filter. Sherlock Holmes said in The Study of Scarlet:

I consider that a man's brain originally is like a little empty attic, and you have to stock it with such furniture as you choose. A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things so that he has a difficulty in laying his hands upon it.

The skillful workman is careful indeed as to what he takes into his brain-attic. It is a mistake to think that that little room has elastic walls and can distend to any extent. Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.

French philosopher Michel de Montaigne felt the same when he said, "More information isn’t necessarily better information but it may falsely increase our confidence. A wise man sees as much as he ought, not as much as he can."

A lot of people seek book recommendations, or a list of writers to follow. But just as important is a list of content you selectively don't read, knowing it's likely to clog your brain-attic.

Here are a three things on my no-read list.

Political opinions disguised as investing analysis

Economics is a close cousin of politics, which is dangerous, because politics is a close cousin of emotional decisions detached from reality.

Not only do most of us have emotional opinions about who should/shouldn't run the country, but we unfailingly overestimate how much influence presidents have over the economy and stock market. When presidents do impact the economy, there's no guessing how markets will respond. Lots of smart people predicted that Barack Obama's spending plans meant surging interest rates and a collapsing dollar. 

Growing the economy means getting everyone to win, whereas politics means getting the opposing party to lose. Rationality melts when you set up this kind of "my team versus yours" dilemma. Psychologist Geoffrey Cohen showed that Democratic voters supported Republican proposals when they were attributed to fellow Democrats more than they supported Democratic proposals attributed to Republicans, and vice versa. Imagine the same part of your brain analyzing investments. It's a disaster.

I like politics, and I love investing. But I run from anything conflating the two.

Time horizons that are far different from mine

I pay no attention to technical analysis -- attempts to predict stock movements by reading charts. Not because I don't think it works, although I doubt it does. But the goal of technical analysis is predicting where stocks will go over the next, say, 30 or 60 days. I have no interest in that stuff because I'm decades away from retirement.

Analysts get into debates about whether a forecast is right or wrong without realizing that something can be relevant to one person and meaningless to another. What stocks do over the next 90 days may be relevant to someone whose paycheck relies on month-to-month returns -- and some people's do. But 90-day returns don't matter for most of us, so we're better off paying no attention to those who attempt to forecast them, as their opinions could make us lose sight of our long-term time horizons. What we sometimes view as a difference in opinion is often just a difference in goals

Excessive length and unnecessary detail

Read enough books, and it becomes apparent that many books didn't need to be books. They could have been articles, even short articles. The economics of the book industry requires length, but most long-form writing has a simple 200-word idea struggling to come out. Joe Wiesenthal of Bloomberg once said, "Every book should be an article, every article should be a tweet, every tweet should be a retweet."

I've become comfortable saying, "OK, I got the point," when reading both books and articles -- and feeling no guilt about moving on.

Thomas Piketty made waves with this 700-page book on income inequality, Capital in the Twenty-First Century. It was called groundbreaking, influential, and something that can shape economic policies around the world. But the average reader, according to Kindle data, read 2.4% of the book before giving up. 

Charlie Munger once said: "Most books I read I don't finish the first chapter. I'm not burdened by awful books."

Even great books -- as I'm sure Pikkety's was -- can often be closed well before the last chapter while still capturing the main ideas. This gives you more time to think deeply about those main ideas, and frees up time to tackle new topics that can improve your knowledge more than drilling down into details of the previous book. You probably won't remember the details anyway. The big points are what stick. 

For more:

How to read financial news

What I read (and why)

Hard truths for investors to wrap their heads around

The agony of high returns

Contact Morgan Housel at The Motley Fool has a disclosure policy.