Gamma Quest Trilogy:  Book 1 (X-Men and The Avengers): (By Greg Cox) When the Scarlet Witch and Rogue disappear under mysterious circumstances, each team's search leads them to more questions that naswers.  When the X-Men appear to attack a government installation, the Avengers must track them down and the truth behind the abductions. (SOURCE: Book Jacket)

Gamma Quest Trilogy:  Book 2 (X-Men and The Avengers): (By Greg Cox) The two teams join forces to find their missing teammates.  With the helpof the Hulk, they learn at last that their foe is the deadly leader.  But the search for gamma-powered evil genius proved more difficult than the two teams can imagine, for the leader has the awesome power of Gamma Sentinerls behind him- and another surprising ally. (SOURCE: Book Jacket)

Gamma Quest Trilogy:  Book 3 (X-Men and The Avengers) (By Greg Cox) The two teams along with the Hulk have joined together and traced the deadly leader to his base on the moon.  But the gamma-powered genius's plans may be more than even they can handle, for the Leader has brainwashed Rogue, Wolverine and the Scarlet Witch.  With them, the Gamma Sentials, his own brilliance, and another mysterious ally at his side, the Leader may be able to defeat the combined forces of Marvel's greatest super-teams.  (SOURCE: Book Jacket)

Jewels of Cyttorak, The:  (By Dean Wesley Smith)Since bonding with the ruby of Cyttorak, Cain Marko became the unstoppable force known as the Juggernaut - and one of the X-Men's most vicious foes!  But an archaeological dig reveals a fragment of the one thing that might be able to stop Huggernaut: an emerald from the same dimension of Cyttorak.  Now a vicious billionaire named Service intends to gather all fragments of the emerald, which will grant him absolute power, unless the X-Men can stop him.  But each use of the emerald causes the Juggernaut pain - and he won't stand it.  > (SOURCE: Book Jacket)

Magneto: The Chaos Engine Book 2  (By Steven A. Roman and Mark Buckingham) One week: That was all the time given to the X-Men to correct a universe-threatening flaw after Roma, Supreme Guardian of the Omniverse, discovered that unknown forces had severely altered the structure of the heroes' home dimension. It hadn't taken them long to track down the source of the disruption: the tyrannical Doctor Doom, in possession of the Cosmic Cube -- a device that allows its owner to twist reality and create their personal vision of a perfect world. (SOURCE: Amazon.ca)
Mutant Empire: Sanctuary Book 2 (By Christopher Golden) Magneto has taken over the entire Island of Manhattan and declared it a haven for mutants.  Ruled by Magneto and his followers, enforced by reprogrammed Sentinels - this is the first step to his ultimate goal of world domination.  Only the X-Men stand in the way of that happening and they are trapped in space while mutants from all over flock to Manhattan and take Magneto's side against the X-Men.  (SOURCE: Book Jacket)

Mutant Empire: Salvation Book 3 (By Christopher Golden) Manhattan belongs to Magneto and his followers.  Half the X-Men have been captured, and Magneto's law is enforced by an ever growing army of mutants and Sentinels.  The remaining X-Men must stop Magneto by turning the Sentinels against him and by defeating the man himself.  To do that, they must join forces with the US government - who view the X-Men as being as mush of a menace as Magneto - and with one of their oldest foes, the Juggernaut.  (SOURCE: Book Jacket)

Red Skull: The Chaos Engine Book 3  (By Steven A. & Timmons, Stan Roman) The last installment in the the Chaos Engine series as some of the X-Men try to prevent their dimension from being destroyed.

Soul Killer (By Richard Lee Byers) The demon lord Belasco plans to use Rogue to bring the evil Elder Gods to Earth. The X-Men and their sister team Excalibur must stop him before Rogue's very soul is destroyed. Their unexpected--and untrusted--ally is the lord of all vampires: Dracula! And the Count always has a more sinister agenda up his sleeve. (SOURCE: Amazon.ca)