It was confirmed in the Wazemonogatari light novel, the second light novel in the off season series, that NisiOisin will be writing two other light novels for the off season series. The following novels are titled Nademonogatari and Musubimonogatari. Now from what has been said both of those light novels will be released sometime this year but with new specific release date announced just yet. An image showcasing the announcement will be showcased later on in the article as well mind you. Now the light novel series overall which is written by NisiOisin is essentially split up into three different novels with a plethora of side stories and adaptions from the novels themselves. The first one to release is Monogatari series: First Season which released between November 1st 2006 and ended July 28th 2010 with 6 volumes, Monogatari series: second season its sequel would later release October 27th 2010 and ended December 20th 2011 releasing 6 volumes as well. Finally is Monogatari series: Final season which released between September 28th 2012 and ended September 18th 2014 releasing 6 volumes.
Now below is a plot summary of the series quoted from MAL:
The story centers on Koyomi Araragi, a third year high school student who has recently survived a vampire attack, and finds himself mixed up with all kinds of apparitions: gods, ghosts, myths, and spirits.