Given that we're in a forum where computer science and engineering topics are often discussed, I find it odd that anyone would suggest this.
You have a limited resource (time). Whenever you have a limited resource, there are tradeoffs in how you spend it. Unless exhaustive search is feasible, there is indeed a tradeoff between depth and breadth.
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.
Emphasis on quotes. Most of that novel is an abusive relationship, from what I hear.