- Under Space
- Under Stars
- Under Strange Suns
- Under Test
- Under the Abbey's Angels
- Under the Alaskan Ice
- Under the Amoral Bridge
- Under the Ancient Suns
- Under the Andes
- Under the Black Clouds
- Under the Blackberry Vines
- Under the Blood Moon
- Under the Blood Red Moon
- Under the Blue
- Under the Blue Sun
- Under the Bones
- Under the Bough
- Under The Broken Sky: The Final Book of the Secret Keeper Series
- Under the Burning Sun
- Under The Cover of Wicca
- Under the Crimson Sun
- Under the Curse of the Lich Queen
- Under the Dark
- Under The Darkness
- Under the Desert Sky
- Under the Devil's Wing
- Under the Dome
- Under the Erotic Moon
- Under the Flickering Light
- Under the Full Moon
- Under the Goddess' Eye: A Collection of Short Stories
- Under the Golden Sun: Part One: Tears of Lace
- Under the Golden Sun: Part Two: Colored Ice
- Under the Great Bear
- Under the Green Star
- Under the Gun
- Under the Heel of the Aether Imperium
- Under the Hill
- Under the Ice
- Under the Ineffable Sky: Romances from the Future Earth
- Under The Knife
- Under the Knife (From the Desk of Col. Garrett Ross)
- Under the Light: Sandes Chronicles Book 1
- Under the Lilacs
- Under the Moon
- Under the Moon Bundle
- Under The Moonlight
- Under the Moons of Gehenna
- Under the Mountain: Book III of The Sword of Bayne
- Under the Mountain: Book Two of the Hawkridge Chronicles
- Under the Papadome
- Under the Polar Star: The Young Explorers
- Under the Radar: A Tale of Super City
- Under the Radar: The Blake Hemlock Chronicles
- Under the Rainbow
- Under the Red Dragon: A Novel
- Under the Rising Sun
- Apocalypses: Under The Rose
- Under the Rose
- Under the Rushes
- Under the Satyr Moon
- Under the Sea: A Short Story Anthology, Vol. 1 (Summertime Myths and Magic)
- Under the Sea to the North Pole
- Under the Setting Sun
- Under The Shell
- Under The Skin
- Under the Skin
- Under The Southern Cross
- Under the Spinodal Curve
- Under The Stars Of Faerie (Monkey Queen Book Three)
- Under the Stone of Destiny
- Under the Sun
- Under the Sunset
- Under the Sunset and Other Stories
- Under the Tiger's Claws: A Struggle for the Right
- Under the Toadstool
- Under The Tree That Owns Itself
- Under the Veil: A Gay-Ass Fairytale
- Under the Vultures' Moon
- Under the Willow Tree
- Under The Willow Tree
- Under the Willow Tree
- Under the Wolf Moon
- Under the Wolf's Shadow
- Under the World
- Under two Moons
- Under Two Moons: Paradisi Chronicles
- Under underjorden
- Under vingarnas skugga
- Under Western Eyes
- Under Witch Aura
- Under Witch Curse
- Under Witch Moon
- Under Your Skin
- Under Witch Moon
- Under Your Skin
- Underboss Raphael
- UNDERBREAK
- Undercaffeinated and Overexposed
- Undercity
- Undercity Chronicles 1
- Undercover für den Dominus
- Undercover Goddess
- Undercover Gorgon: Episode #0 — Becoming (A Mt. Olympus Employment Agency Miniseries)
- Undercover Gorgon: Episode #1 — Witches War (A Mt. Olympus Employment Agency Miniseries)
- Undercover Gorgon: Episode #2 — Lost & Found (A Mt. Olympus Employment Agency Miniseries)
- Undercover Madness
- Undercover Magic
- Undercover Snake
- Undercover Truths: Undercover Lies
- Undercover Unicorn
- Undercovers
- Undercurrents
- Underdead with a Vengeance
- Underdog Chronicles
- Underdogs
- Underestimation
- Undergrad Elementalist
- Underground Bride
- Underground Heat Complete Series
- Underground Man
- UNDERGROUND MARKET
- Underground: A Dungeon Crawler Adventure
- Underground: An Egyptian Mythology Urban Fantasy
- Underground: Revoluce
- Underground: The Day of the Sun
- Undergrowth
- Underhive
- Underhive Apex
- Underlay
- Undermajordomo Minor
- Undermarch
- Undermind
- Underneath the Bough: A Book of Verses
- Underneath the Sheets
- Underscore_
- Undersea Fleet
- Undersea Quest
- UnderSilver
- Understanding the Misunderstood