- Unicorns I
- Unicorns II
- Unicorns of Balinor: By Fire, by Moonlight (Book Four)
- Unicorns of Balinor: Shadows Over Balinor (Book Eight)
- Unicorns' Opal
- Unida a la bestia
- Unida a los Ciborgs
- Unida a los guerreros
- Unida a los Viken
- Unida aos Guerreiros
- Unida com a Fera
- Unidentified
- Unidentified Flying Objects: Nine Classic Sci-Fi Stories
- Unidentified Funny Objects
- Unidentified Funny Objects 2
- Unidentified Funny Objects 4
- Unidentified Funny Objects 5
- Unidentified Funny Objects 7
- Unidentified Funny Objects 8
- Unidentified Texas Objects
- Unidentified Underground Object: The Sleeping Alien Awakens
- Uniesienie
- Unification
- Unification In 6066
- Unification: Rise of the Thunderblade
- Unified Fields
- Unikum ordinarium: СУПЕРМЕН ПОНЕВОЛЕ
- Unintended
- Unintended Consequences
- Unintended Guardian
- Unintended Heroes
- Unintended Matter
- Union
- Union Forever
- Union of Fire
- Union of Renegades
- Union Space: From the Ashes a Fire Shall Be Woken
- Union Space: In the Beginning
- Union Space: The Path Less Travelled
- Unique Martial Sovereign
- Uniqueness Counts
- Unit 6
- Unita alla bestia
- UnitArmy
- Unitary
- Unite and Conquer: A Royal Academy at Osyth Story
- United
- United As One
- United Moon Colonies
- United Souls
- United Star Systems Marines
- United States Of Apocalypse 2: Razed Country
- United States Of Apocalypse 3: Divided Nation
- United States Space Force 1980
- United We Fall
- United We Stand
- UniteDead Kingdom
- UniteDead Kingdom 2
- Unity
- Unity of Elements
- Unity of Seven
- Unity Through Chaos
- Unity: Book One of Ascension
- Unity: Krinics Series: Book 3
- Unité et diversité: le combat des diwallers
- Univaya
- Univers Parallèles - Faith
- Univers Tetralogie
- Univers transcendental
- Universal
- Universal Dickhead
- Universal Income
- Universal Language
- Universal Legacy - Tome 1
- Universal Links
- Universal Maintenance
- Universal Mud
- Universal War
- Universe Diplomat
- Universe For Sale
- Universe Hunters: Taken
- Universe Launch
- Universe of Fear
- Universe Olympics
- Universe Pathways
- Universi
- Universe Pathways
- Universi
- Universi in fuga - Prima parte (Urania)
- Universi in fuga - Seconda parte (Urania)
- Universi in guerra
- Universi Mondi
- Universi sconosciuti
- University Past Time
- Universo e altre periferie
- Universo Em Expansão - Casamento
- Universo Em Expansão - Intempéries
- Universo Em Expansão - Travessia
- Universo in scatola
- Universo Rownsders
- Universo senza luce (Urania)
- Universos en expansión
- Universos paralelos
- Universums ark
- Universums mörka hemlighet
- Universus Respondet: Fermi's Paradox Answered—a Novel
- Univerzita výnimočných 3 - Odveta
- Unjust Theft
- Unjustified Favor
- Unknown Alien Language
- Unknown Country, The Trilogy
- Unknown Earth Volume 2
- Unknown Elves
- Unknown for a Reason
- Unknown Guardians
- Unknown Horizons
- Unknown Journey
- Unknown Man
- Unknown Object
- Unknown Place, Unknown Universe
- Unknown Reality
- Unknown Relams
- Unknown Revenge
- Unknown Science Stories
- Unknown Taste
- Unknown Worlds
- Unkontrollierbare Sprünge
- UNLAWFUL RESTRAINT