A Noble Undertaking

Kings, earls, dukes, are all welcome. But absolutely no real nobility (in other words, books about Queen Victoria or Richard III or Marie Antoinette are right out, that would be too easy)!

The Duchess of Jermyn Street, by Daphne Fielding
The Princess Casamassima, by Henry James
Odilon Redon: Prince of Dreams, 1840-1916, by Douglas W. Druick
The Queen's New Shoes, by Adwoa Badoe
The Mambo Kings Play Songs of Love, by Oscar Hijuelos

The Count of Montecristo by Alexandre Dumas
The Prince by Niccolo Machiavelli
The Prince and the Pauper by Mark Twain
The Red Baron by Peter Kilduff
The Countess Kathleen by W. B. Yeats

The Duchess of Duke Street : a novel by Mollie Hardwick
The Tin Princess by Philip Pullman
Babar the King by Jean de Brunhoff
The Little Prince by Antoine de Saint-Exupery
The Prince of Tides by Pat Conroy

Harry Potter and the Half-Blood Prince by JKR
All The King's Men by Robert Penn Warren
God Emperor of Dune by Frank Herbert
Nine Princes in Amber byRoger Zelazny
The Sport of Queens; the autobiography of Dick Francis

Lord Emsworth and others by P.G. Wodehouse
Lord Mullion's secret by Michael Innes
Lord Jim by Joseph Conrad
Lords and ladies by Terry Pratchett
Lord Hornblower by C.S. Forester

Little Princess
The Princess Bride
The light princess
The Tin Princess
Heir to the Empire

Lady Knight
Sorcery and Cecelia or The Enchanted Chocolate Pot: Being the Correspondence of Two Young Ladies of Quality Regarding Various Magical Scandals in London and the Country
Trickster's Queen
The Will Of The Empress

The King of Torts by John Grisham
The Princess Bride: S Morgenstern's Classic Tale of True Love and High Adventure by William Goldman
The Sweet Potato Queens' Big-ass Cookbook (and Financial Planner) by Jill Conner Browne
Queenie Peavy by Robert Burch
The Lord of the Rings by J.R.R. Tolkien

Queen's Gambit by Walter Tevis
Lord Demon by Roger Zelazney
Prince of Wolves by Susan Krinard
His Grace of Osmond
and
A Lady of Quality byFrances Hodgson Burnett

The Faerie Queene by Edmund Spenser
The Snow Queen by Hans Christian Andersen
The princess of Burundi by Kjell Eriksson
Lord of the silent by Elizabeth Peters

and this one doesn't quite fit, but it's close and I need it to round out my 5:
Ratking by Michael Dibdin

A Treasury of Royal Scandals: the Shocking True Stories of History's Wickedest, Weirdest, Most Wanton Kings, Queens, Tsars

the Unseen Queen

the Courtship of Princess Leia

the Grey King

the Joiner King

The Coming of the King by Nikolai Tolstoy
Queen's Play by Dorothy Dunnett
The Changeling of Monte Lucio by Violet Needham
King Hereafter by Dorothy Dunnett
Lord of Fire by Galen Foley

Lord Chesterfield's Letters
Lady Chatterley's Lover by D.H. Lawrence
Mistress of the Elgin Marbles: A Biography of Mary Nisbet, Countess of Elgin by Susan Nagel
Seven Gothic Tales by Isak Dinesen aka the Baroness Blixen
Justine by the Marquis de Sade

Bad Prince Charlie by John Moore
The King of the Castle by Victoria Holt
The Summer Knight by Jim Butcher
The Golden Pharaoh by Peter Danielson
King Solomon's Mines by H. Rider Haggard

A Knight in Shining Armor by Jude Deveraux
The Wolf King by Alice Borchardt
Return of the King by J.R.R. Tolkien
The Lord of the Rings by J.R.R. Tolkien (yes I know Return of the King is part of the trilogy. I have both the individual books and a combined volume)
The Princess Bride

Lord of Emperors by Guy Gavriel Kay
The High King by Lloyd Alexander
The Baron in the Trees by Italo Calvino
The Citadel of the Autarch by Gene Wolfe
Project Pope by Clifford D. Simak

King of the Murgos by David Eddings
Queen of Demons by David Drake
Dark Prince by David Gemmel
A Clash of Kings by George R. R. Martin
Rise of a Merchant Prince by Raymond E Feist

King Rat
Thine is the Kingdom
Valleys of the Assassins by Dame Freya Stark
Pocahontas and the Powhatan Dilemma
Feminist Activism in the SUPREME Court

King John of Canada by Scott Gardiner
The Thief Lord by Cornelia Funke
The Prince in Waiting by Christopher John
The Two Princesses of Bamarre by Gail Carson Levine
Warlord by Elizabeth Vaughan

Prince Bertram the Bad by Arnold Lobel
Lord of the Dance by Robin Lloyd-Jones
Knight of Shadows by Roger Zelazney
The Light Princess by George MacDonald
His Grace of Osmonde by Francess Hodgson Burnett

Temeraire: His Majesty's Dragon by Naomi Novik
Lords of Discipline by Pat Conroy
The Middle Kingdom by David Wingrove
Lord of the Flies by Harold Bloom
Kings Row by Henry Bellamann

My Last Duchess by H K Bannerman
The Man Who Would Be King by Rudyard Kipling
The Duchess of Malfi by John Webster
The Last King of Scotland by Giles Foden
The Snow Queen by Joan D Vinge

Nolan Ryan, Strike-out King
King Blood
The winter queen
The Duke's Children
Princess Casamassima

The Chili Queen by Sandra Dallas
The Mysterious Flame of Queen Loana by Umberto Eco
The Queen Bee of Mimosa Branch by Haywood Smith
The One-Armed Queen by Jane Yolen
Claudia, Queen of the Seventh Grade by Ann M. Martin

The Short History of a Prince by Jane Hamilton
Prince Caspian by C.S. Lewis
Lord John and the Private Matter by Diana Gabaldon
The Lady and the Unicorn by Tracy Chevalier
The Emperor of Ocean Park by Stephen L. Carter

Royal Family

The Briar King by J. Gregory Keyes
The Once and Future King by T. H. White
Queen City Jazz by Kathleen Ann Goonan
Queen of Angels by Greg Bear
Henderson, the Rain King by Saul Bellow

The Court & Hangers On...

Count Zero by William Gibson
The Emperor of Gondwanaland and Other Stories by Paul Di Philippo
Lord Foul's Bane by Stephen R. Donaldson
The Knight by Gene Wolfe
Royal Assassin by Robin Hobb