The House of Mystery by James G. Lynch (Jimmy Joe) 2018 (1 rating)

How the West Was Lost, by H.W. Williams

Hyper Rift by CKS Studios 2015 (2 ratings)

I Contain Multitudes by Wonaglot 2021 (5 ratings)

Impact!, by Laurence Creighton (1992)

In cerca di Tesla, by High school "Guglielmo Marconi" of Imperia (2016)

In Search of the Holy Grant Cheque, by David R. Stone (1985)

In Search of the Lost Valley, by Unknown (1988)

In the Clutches of Torrik, by John Nelson (1985)
(1 rating)

Infidel by Michael Berlyn 1983 (53 ratings)

Infinite Adventure by B.J. Best (writing as “A. Scotts”) 2021 (8 ratings)

The Institute by Jyym Pearson and Robyn Pearson and Norman Sailer 1981

Into The Briny Blue, by SJL (2011)

Jake English and the Secret of the Soul, by dirkar (2017)

Jazz Age by Nicola R. White 2019 (1 rating)

The Jewel of Knowledge, by Francesco Bova (1999)
(5 ratings)

A Killer Headache by Mike Ciul 2012 (20 ratings)

Kingdom of Kull, by Jeremy Williams (1987)

The Knight's Quest by Mike Farley 1983

The Knot by Richard Goodness writing as The water Supply writing as Gevelle Formicore, Tarquin Segundo, and Willershin Rill 2020 (3 ratings)