Reading Room
From Halopedia, the Halo wiki
Reading Room is an achievement in Halo: The Master Chief Collection. It is unlocked by beating the 25,000 point par score on The Library. The achievement is worth 10 Gamerscore. Though it can theoretically be unlocked on any difficulty, more points are awarded in campaign scoring when playing on higher difficulties.
Trivia
The name of the achievement is a reference to the typical meaning of the word "library".