Masks and Monsters collects two short cross-over arcs into one trade paper back. The first has Hellboy battling Lovecraftian-cultist Nazis with Batman and Starman. The second has Hellboy and The Ghost crossing paths.
Hellboy / Batman / Starman is a strange story. While more of a Hellboy story than Batman or Starman the writing is rougher than a typical Hellboy story; some fairly blunt exposition dialog and forced character interaction serves to highlight the jarring disconnect between the titular characters. Of the two chapters the second half with Starman is the better half. On the plus side: Mignola drawing batman.
Hellboy / Ghost is two stories fighting for screen time; the story of a woman haunted and haunting, and another episode of evil and mysterious powers trying to get hold of Hellboy’s hand. Unfortunately both stories are weakened rather than strengthened by the other. The unoriginality of Hellboy’s role in the story effectively relegates Hellboy to merely the reader’s viewpoint in a surreal identity story.
Overall a volume better suited to the curious Hellboy completist than a must get (unlike The Amazing Screw-on Head).