I don't necessarily disagree with your conclusion but your analysis is an oversimplification. It's possible reading broadly across domains results in deeper individual domain expertise by enabling cross-fertilization between the domains. So the relationship between depth and breadth isn't necessarily inverse or linear.

Take the recent solution to the Kadison-Singer problem. A group of relative outsiders with comparatively little mathematics expertise solved a long standing problem using techniques from their own field, computer science. The depth they achieved in math exceeded that of people who focused solely on the math. And similarly they achieved more in their own field by tackling problems from other fields.

Obviously there's a very tight conceptual relationship between those two fields even if that isn't always the case institutionally. But I think you can easily find examples where knowledge from dramatically different domains contributed to some paradigm shift, breakthrough, or other significant achievement.

Depth and breadth, in this case, are not opposite directions on a straight line. They are vectors that only appear oppositional when viewed under specific time constraints. The more prolific a reader you are, the more efficiently you read, and thus your higher throughput dramatically compresses time.

If we're to speak about very specific increments of time and units of reading material -- say, you get to read N books over 1 week -- then sure, the zero-sum argument holds. But a lifetime is so much time, offering so much opportunity to the experienced reader, that time is almost effectively lifted as a constraint.

The only zero-sum quantities in this case are time and number of books. Depth and breadth of subject matter are better described as characterizing subcategories of #_books.

>Depth and breadth, in this case, are not opposite directions on a straight line

humans have limited memory, we are not machines. How many books can you remember, and not just in a vague sense, but lines, tone, structure?

Nabokov made a similar statement as the author claimed that the only good reader is a re-reader. Nobody can genuinely remember more than a few books and be familiar with them, if you read hundreds of books at the end of the year you might as well have read nothing. But every time you reread a great work, you learn something new and free your mind up to discover even more things about it.

The very best musicians will often study their favourite pieces compulsively. They have an intimate relationship with them that others have not.

I am very sympathetic to the message of the author because we seem to be living in an age where people attempt to measure literacy on a scoreboard by counting how much books they've read. Obviously this is as doomed of an attempt as being in a hundred relationships at the same time.

A good friend of mine teaches Russian literature, and when he talks about a book like The Brothers Karamazov he can get so much more out of one book than I get out of reading 50. That is something to me that resembles genuine understanding.

Learning how to find what you will think are "great books", I think, is more important than the raw number of books. Having people that know you well and are good readers themselves can be a great resource. Also, the ability to abandon a long book after an hour of reading can be difficult for some but quite useful if you find your reading time limited.