- X de Sodoma: Duología completa
- X de Sodoma: El Mundo Termina por Ti
- X de Sodoma: Una Canción para el Fin
- X Marks the Spot
- X My Heart
- X RALPHI INDRAE. Neparastā ekspedīcija
- X Tales for O Minds
- X The Unknown
- X War Trilogy
- X War: Incursion
- X War: Infestation
- X War: Infiltration
- X's For Eyes
- X-Finney Strikes Again
- X-Men
- X-Men - L'affrontement final
- X-Men - Le commencement
- X-Men 2
- X-Men Origins Wolverine
- X-Men. Saga Mrocznej Phoenix
- X-Troller
- X6
- X67 Marceline
- The Hammer of Asttar
- Xamã
- Xan's Feisty Mate
- Xana-La
- Xander and Des
- Xander vol.1 Transmutation
- Xander's Essence: Part One
- Xander's Powerful Growing Pains
- Xandra's Legacy
- Xanthan Gumm
- Xanthan Gumm
- Xanthe and the Seaman
- Xarax
- Xares: Final Countdown
- Xaromar
- Xarthan Wars: Invasion
- Xarxium
- Xavier
- Xavras Wyżryn i inne fikcje narodowe
- Xbola
- Xchange
- XCULP: The Great Reduction and Procreation
- Xeeh
- Xeeta
- Xenatha and the Ogs
- Xenation: Draw the Line
- Xeno
- Xeno Fiction: More Best of Science Fiction
- Xeno Sapiens
- Xenofall
- Xenoforming - prvý stret
- Xenogeneic: First Contact
- Xenoman
- Xenophobe
- Xenos
- Xenostorm: Rising
- Xenovation
- Xenowealth: A Collection
- Xenuh e o Destino de Agren
- Xero
- Xeón
- Xhazul's Box: The Rainbow Sphere
- Xiao
- Xiaxan Fox
- XiFiSy
- XII - Il segno dei giusti
- XIII
- Xiloeh y otras historias
- XIN: The Veiled Genocides
- Xipilik Hunters
- Xivaari
- Xkalibur
- Xmas @ Camelot II
- Xmas Wars - Crazy about Han
- Xmas Wars: Pazza di Han
- Xmouse Downunder
- XNOR
- Xoc de Reis (Cançó de gel i foc 2)
- Xolotl Strikes!
- Xorés: Book 3
- Xperiment
- Xperts: E-Smog
- Xperts: Mindwave
- Xperts: The Paracommunicator
- Xperts: The Paradoppelganger
- Xperts: The Paranet
- Xperts: The Parashield
- Xperts: The Parawarriors
- XPERTS: The Telekinetic
- Xterra Conspiracy
- Xterra Escape
- Xto Ferens
- Xtoriez