Seth asks the above question. I have a couple of thoughts:

1. It’s hard to write a book that’s easy to read. As Seth points out, it’s a Venn diagram situation: you’re looking for the overlap between three groups of people: those who know the material, those who can write well, and those who are willing to put in the effort to write a book.

2. Some subjects are so urgent that they’re worth writing–and reading–about even if hard to read. For example, if you’re a terrorist and want to build an A-bomb (or, to use another example, if you’re a social scientist and you want to use quantitative methods), sure, you’d prefer clear instructions, but something that’s hard to read is still much better than nothing.

3. What’s hard for you to read might be easy for somebody else. An extreme example is foreign language or the passage of time. But, beyond that, there’s familiarity. For example, I find the news section of the newspaper much easier than the comics to read. The comics are much simpler, but I’m not familiar with them, and to read them I have to enter all these different stories. In contrast, news stories follow a predictable pattern: drought in the Great Plains, people blowing each other up in the Middle East, and so forth.

4. Standards differ. Bayesian Data Analysis is considered by many to be well-written but it’s much less easy to read than Data Analysis Using Regression and Multilevel/Hierarchical Models, which in turn is, I’m sure, much less easy to read than the collected works of Len Mlodinow. But, then again, Mlodinow is harder to read than Stephen King. If Stephen King wants to write statistics books, that’s fine, but I’m afraid that would wreck things for the rest of us. It would set the bar too high.

5. And, of course, some people write books to be hard to read on purpose. James Joyce and so forth. If you, like me, aren’t a big James Joyce fan, just pick your favorite writer who you find challenging to read (in a good way).