The Reading Steiner is a term referring to Rintaro Okabe's ability to, after switching world lines, retain his memory of events that have occurred (from his point of view) before the switch.
World lines can be switched by altering the past, for example through the use of D-mails.
While no other members of the cast have this immediate knowledge of a switch having occurred or any recollection of what happened in another World Line, they seem to regain fragments of these memories occasionally.
For example, Faris remembers sending the D-Mail that prevented her father's death after talking to Rintarou in her apartment, and Mayuri, visiting her grandmother's grave in the Alpha timeline, speaks of "Nightmares" in which she dies in a multitude of ways.
The ability plays a major role in the plot, most prominently in allowing Rintarou to undo the changes caused by the D-Mails and not losing track after each switch.
In the anime, there is a visual distortion every time a Reading is activated, usually following the sending of a D-mail.
- The movie Steins;Gate: Fuka Ryouiki no Deja Vu features the Reading Steiner as an important plot element, as Kurisu and Mayuri use recollection of the pre-Steins Gate world lines to piece together information about Rintarou.