YMMV / Strange Matter

• Darker and Edgier: Deadly Delivery is much darker in tone than most other books in the series. Things start off innocently enough with a mischevious poltergeist being delivered in the mail, but then he transforms the protagonists' house into his castle and we learn that he's the spirit of a monstrously tyrannical medieval ruler, Baron Oscar Bluzher. His home includes the ghost of his mother (whose tongue he cut out for yelling at him during a banquet), the ghost of his sister (whom he beheaded for not approving of his marriage), his mentally and physically handicapped brother that he locked in secret room and acts bestial (due to never being around other human beings) and a tower filled with ghosts (among them toddlers and an infant) that he offered "sanctuary" to by sealing them in alive to starve to death. The worst part, though, is that the middle-aged baron plans to "marry" the middle-school aged female protagonist in a wedding chapel which he had decorated with the bones of his former victims due to wanting to to warn his wives not to disobey him. Granted, she doesn't have to worry about what being married to him would be like since he plans to throw her off the balcony as soon as the ceremony is over (as he did to his first wife) but that doesn't make it better!
  • Strange Forces in general was much darker than the main series. The first ever onstage death in Fairfield had occurred by chapter three of the first book, in which a teenager gets rapidly aged to death.
• Fridge Brilliance: Re-reading Book 6, Bad Circuits, you'll notice a lot of hints towards the twist ending that would be completely dismissed on first reading. Stephanie mentions that she thinks very logically, she mis-understands a figure of speech Daniel uses, survives being thrown through a glass skylight with no injuries, is surprisingly strong, and mentions several times not feeling pain when she would normally expect to. All make much more sense knowing that Stephanie is actually an android.
• Older Than They Think: Strange Forces basically did the "protagonists from previous books team up to stop a big threat" concept long before Goosebumps Horrorland did.
• Unintentionally Unsympathetic: Joe from Something Rotten steals some crystal specimens from a marked off section of the local caverns, and it ends up releasing a bunch of acidic blob monsters called Derros. While Joe works hard to right his mistakes, the ending of the book can be pretty frustrating since Joe's selfishness resulted in his neighbor's dog being gravelly injured, and one guy who was Joe's friend gets eaten alive with Joe never really receiving an appropriate punishment for his actions.
• What Do You Mean, It's for Kids?: See the entries regarding Deadly Delivery above.
• The Woobie:
  • Ross from Second Sighting is just a poor kid being hunted down by government agents because his stepmom happens to be an alien. The kid spends most of the book terrified trying to find his parents, and has to rely on help from total strangers (Sean and Patty, Marlon Walker) to find them.
  • Rilo Buru, a Defector from Decadence monster in Strange Forces who was forced to watch as his entire tribe was killed off by the Collector who enslaved him, and, despite his good nature, is constantly in danger of attacking his human friends due to the Collector's implanted Restraining Bolt. His giant sloth friend also counts, only wanting to return to living a harmless existence sunning himself in the South American river that he lived in before the Collector abducted him and forced him into slavery.