Extensive Reading is a resource heavy technique used in second language acquisition in which language learners read large amounts of texts for enjoyment, with the expectation that they will improve their vocabulary and fluency as a result of exposure to the written language. Narrow Reading is a similar technique in which the texts have a common element--such as theme or author--to expose learners to more textual redundancy. This literature review concludes that the evidence suggests both techniques can be effective and valuable to second language learners and foreign language learners. It is also suggested that librarians should be aware of these techniques in order to ensure that collection policies and advice to patrons can assist learners with creating their own Extensive Reading or Narrow Reading programmes. Libraries should also consider working in co-operation with each other to supply Extensive Reading or Narrow Reading projects to areas where there is a known need for material in a given language.