In addition to coldtea's excellent list, there's a handful of modern novels that have always stood out for me over the past 30-40 years of reading: The Testam

In addition to coldtea's excellent list, there's a handful of modern novels that have always stood out for me over the past 30-40 years of reading: The Testament of Gideon Mack: https://www.amazon.co.uk/dp/014102335X https://www.amazon.co.uk/dp/014102335X Hard Boiled Wonderland: https://www.amazon.co.uk/dp/0099448785 https://www.amazon.co.uk/dp/0099448785 Walking on Glass: https://www.amazon.co.uk/dp/B002TXZTE8 https://www.amazon.co.uk/dp/B002TXZTE8 The Ginger Man: https://www.amazon.co.uk/dp/0349108757 https://www.amazon.co.uk/dp/0349108757 Perhaps not true cult classics, but they're often titles I've recommended or just buy for friends many times, and go back and re-read periodically.