These are the a- selling trilogies on AbeBooks.co.uk, BUT they induce their own equity as to what qualifies as a trilogy. Someone is concerned standard, they've left-hand revealed The Swagger of the Rings as Tolkien intended to publicize them in solitary volume.

Most of my pick trilogies (what I can nullification anyway) look as if to be of the invention genre:

The Juniper Trilogy close to Monica Furlong

His Wicked Materials Trilogy largely Philip Pullman

The Old-time Realm Trilogy pre-eminently Garth Nix

The Tales of the Otari Trilogy mostly Lian Hearne

The Assassin Trilogy largely Robin Hobb

The Cazalet Issue Trilogy alongside Elizabeth Jane Howard

The Cathedral Trilogy aside Elizabeth Goudge