Making trilogies

In my apartment in Gothenburg, this system lived for quite a long while: I arranged as much as possible of the fiction in trilogies. Some of them came in trilogies (or tetralogies etc) to begin with, but the main attraction were the trilogies I constructed myself.

Examples:

The Books-Are-Sexy trilogy
Making Love: A Conspiracy Of The Heart Marius Brill
Hyssj Jean-Marie Gourio [original title: Chut!]
Small World: An Academic Romance David Lodge

The Silver Screen trilogy
Blonde Joyce Carol Oates
The Book Of Illusions Paul Auster
Laterna magica Ingmar Bergman

The Superhero trilogy
Watchmen Alan Moore & Dave Gibbons
The amazing adventures of Kavalier & Clay Michael Chabon
Fury Salman Rushdie

The Falling For Fey trilogy
Tithe Holly Black
Thomas The Rhymer Ellen Kushner
Faunen Anna-Karin Palm

The & diptych
Mason & Dixon Thomas Pynchon
Jonathan Strange & Mr Norrell Susanna Clarke

The Odyssey trilogy
The Odyssey Homeros
Ulysses James Joyce
Strändernas svall Eyvind Johnson

The Coming Unstuck in Time tetralogy
Livsdagen lång Eyvind Johnson
The books of Abarat Clive Barker
Slaughterhouse-5 Kurt Vonnegut
Ferdydurke Witold Gombrowicz

The Everything Flows tetralogy
Dagarnas skum Boris Vian [original title: L'ecume des jours]
The waves Virginia Woolf
The shipping news E. Annie Proulx
Lighthousekeeping Jeanette Winterson

The Of Man and Wolf trilogy
Zen and the art of motorcycle maintenance Robert M. Pirsig
Stäppvargen Hermann Hesse [original title: Der Steppenwolf]
Varulven Aksel Sandemose

The Metaphysical Recreation trilogy
Human croquet Kate Atkinson
The stars' tennis balls Stephen Fry
The divine comedy Dante Alighieri

The What We May Have To Do trilogy
Pesten Albert Camus [original title: La peste]
Kallocain Karin Boye
Fahrenheit 451 Ray Bradbury

The Boy/Girl trilogy
The PowerBook Jeanette Winterson
Orlando Virginia Woolf
Drottningens juvelsmycke Carl Jonas Love Almqvist

The castling trilogy
An instance of the fingerpost Iain Pears
Bernard Foys tredje rockad Lars Gustafsson
The New York trilogy Paul Auster

The Please Allow Me to Introduce Myself books
En diaboliad Mikhail Bulgakov
Mästaren och Margarita Mikhail Bulgakov [original title: Ма́стер и Маргари́та]
Dokument rörande spelaren Rubashov Carl-Johan Vallgren
Good Omens Neil Gaiman & Terry Pratchett

The Min Fader Konungen trilogy
Boken om Pippi Långstrump Astrid Lindgren
Mio, min Mio Astrid Lindgren
Kejsarn av Portugallien Selma Lagerlöf

And so on, and so on, and so on.

A major problem with this system was the inconsistency. Trilogies swelled to become tetralogies, pentalogies etc. Books in "natural" trilogies (as their author intended, dead or not) wanted to be in my constructed trilogies. Books wanted to be in several trilogies at once. And many, many books didn't want to be in a trilogy at all. Something to applaud, naturally, but the system frowned upon it.
This may be the only picture I have, of a part of the shelf:
The shelf's inhabitant is called Moira.