- Under a Painted Sky
- Under a Purple Moon
- Under a Starlit Sky
- Under Alex's Bed
- Under an Apricot Moon
- Under Control
- Under Copp's Hill
- Under dansk flag
- Under Drake's Flag
- Under Falling Skies
- Under Hill (Aos Si, #2)
- Under His Bed
- Under His Spell
- Under Jupiter
- Under kometens hale
- Under Locker and Key
- Under My Bed: Zipto Meets Dubious
- Under My Hat
- Under Plum Lake
- Under Pressure
- Under Pressure With a Squash
- Under Suspicion
- Under Suspicion: A Friday Barnes Mystery
- Under the African Sky
- Under the Arches
- Under the Bed Fred
- Under the Bottle Bridge
- Under the Bridge
- Under the Chilian Flag
- Under the Cover Dog and the Case of the Missing Message
- Under the Cover Dog and the Case of the Strange Noise
- Under the Egg
- Under the Ghost Gum Tree
- Under the Green Hill
- Under the Liberty Tree: a story of the "Boston Massacre”
- Under The Light Of A Full Moon
- Under the Mendips, a Tale
- Under the Mermaid Angel
- Under the Milky Way
- Under The Moon
- Under the Moon Bundle
- Under the Mountain Boxed Set: Books 1-3
- Under the Neon Glow
- Under The Never Sky
- Under the Never Sky
- Under the Never Sky Enhanced Edition (Enhanced Edition)
- Under the Never Sky: The Complete Series Collection
- Under the Persimmon Tree
- Under the Rebel's Reign
- Under the Rose Apple Tree
- Under the Rubble
- Under the Same Sky
- Under the Same Stars
- Under the Screaming Sky
- Under the Screaming Sky Book 1 Red Dragons
- Under the Sea
- Under the Shadow's Eye
- Under the Stars
- Under The Stars Of Faerie (Monkey Queen Book Three)
- Under the Summer Sun
- Under The Stars Of Faerie (Monkey Queen Book Three)
- Under the Summer Sun
- Under the Water
- Under the Watsons' Porch
- Under the Waves
- Under the Waves; or, Diving in Deep Waters
- Under Their Skin
- Under Western Eyes
- Undercover Fan
- Undercover Princess
- Undercover Revenge
- Undercover Witch Academy: First Year
- Undercover Witch Academy: Second Year
- Undercover Witch Academy: Third Year
- Underdawgs
- Underdog
- Underground To Canada
- Underland
- Underlondon - Tome 1
- Underlondon - Tome 2
- Underlord
- Underminity
- Underneath Everything
- Underneath the Sea
- Underpants are Awesome! Three Pants-tastic Books in One!
- Understanding Me
- Undertale: Diary of a Wimpy Human
- Undertale: Diary of Frisk in Snowdin Forest - Through the Forest Part 2
- Undertow