The Case for Narrow Reading is a 4 page paper by Steven Krashin.  In it, he suggests that “It may be that narrow input is much more efficient for second language acquisition.” than the wide anthology style reading tought in most classes. 

The basic idea is that single subjects or individual authors use repeated phrases and a subset of vocabulary making the input more comprehensible.  Comprehensible input makes for better practice and familiarity with grammatical patterns.  He cites the existence of the “first few pages” effect where it is the first few pages of a book that are the most difficult and gets easier after further reading.  He also cites research showing that children who read a series end up being better readers.

In other articles Krashin suggests that narrow reading and narrow listening is best for intermediate learners who are just beginning to grasp the language but have difficulty reading or following conversions.