If you arrange your reading around questions or areas of exploration, you'll end up reading multiple books about the same topic.
That allows you to do a kind of cross-sectional mental econometrics and see which pieces start fitting together.

Read In Clusters

Take reading seriously, develop a passion for it, and view it as part of your practice as a knowledge worker to get ahead, but along the way, have fun doing so!

Have Fun!

Every area you don't give a damn about you probably should read at least one book in. Because the very best book in that area is superb, and you're not going to know what it is. 
So if tennis is something you don't know anything about, well, read Andre Agassi's memoir. That's a wonderful book. You don't have to know about or care about tennis.

Read Stuff You Know Nothing About

The best reading is focused reading, when you're trying to solve some kind of problem. You could aim to answer a specific question, investigate a given author, or scratch an itch of curiosity. 
You want to start with a problem or question when you're reading.

Read To Solve A Problem

Gathering a stack of non-fiction titles to explore a topic is great, but don't neglect fiction. 
Reading fiction is important to understand the cross-sectional variation in humanity, to understand how difficult generalizations can be, to just get a sense of how different social pieces fit together, and to get a sense of different historical eras -- and plus, reading fiction is often just plain flat-out fun.

Read Fiction

Not captivated by a particular book at a particular time? Then on to the next. Just stop reading, put them down. 
There are countless amazing books out there. Don't settle for less than good.

Be Ruthless

At least in the case of nonfiction, if you already know the material, feel free to skip ahead. When you go to read actual books you're like, 'I know that, I know that, I know that,' and you keep on going, and you read much more quickly. 
And that's really the way to read a lot. This also creates a virtuous cycle in which the more you read, the more you'll know, and the more you can skip.

Skim Those Books

How to get smarter isn't mysterious and it isn't complex. The answer has been the same for millennia. Read more (though it's true these days we do now have lots more delivery methods. 
The trick isn't in figuring out what you need to do--it's in actually managing to do it.

Getting Smarter

Economist, blogger, and super reader Tyler Cowen's advice on how to get smarter by reading way more. 