Unlike the first game, Metro 2033, Metro Last Light is not based off of any book, instead being an original story co-written by Dmitry Glukhovsky(the author of 2033).
A feature-length film is currently in production based on the Metro games.
A Redux version of Last Light was released for the Xbox One, PlayStation 4, and PC. This version is largely unchanged from the original released version, but contains improved animations, improved lighting, hidden safe supply caches, and a locked 60fps frame rate on consoles. Metro: Last Light Redux also comes with all previously released DLC, and all of the DLC weapons have been integrated into main campaign.
The third book in the Metro series by main author Dmitry Glukhovsky is planned to be a novelization of Last Light.