According to Holly Black and Tony DiTerlizzi, the text of this story was left for them by three mystery kids. 
 And after spending the first book introducing the world of strange fey creatures, the second book in the Spiderwick Chronicles deals with the first clash with them. "The Seeing Stone" throws our three juvenile heroes into the midst of grotesque and eerie creatures, and despite the book's tiny size, it's a solid little fantasy story. 
 After a rotten day at school, Jared's day actually manages to get worse -- he sees Simon being captured by an invisible force and dragged into the woods. According to Thimbletack, he was kidnapped by goblins -- and now if Mallory and Jared want to save him, they have to use the "lens of stone" to find him (sort of a multi-lensed viewing monocle that lets you see faerie creatures). And Jared is desperate enough to take it. 
 But the lens only allows them to SEE the goblins -- fighting them is a much harder problem, and they only have a short time before the monsters try to EAT Simon. With only the lens and a few small weapons, they venture off into the forest... but there are dangers other than the goblins in the woods nearby, and even if they find him, how can they avoid being captured as well? 
 A wounded griffin, a sludgy lake troll, grotesque toadlike goblins and little leaf-winged grass-haired sprites -- Holly Black and Tony DiTerlizzi certainly up the amount of supernatural goings-on in "The Seeing Stone." And given a late development that allows the kids to see the stranger side of the world, these aren't going to be the last fey creature they encounter in this series. 
 And Black and DiTerlizzi's shared writing style brings this seemingly simple tale to exquisite, creepy life ("Hairless cat-like ears stuck up from their heads, and their teeth were pieces of shattered glass and small jagged rocks"). Though the storyline is pretty simple, the writing weaves a web of subtle, eerie strangeness around the seemingly ordinary circumstances, and makes it almost believable that evil goblins might be in the woods near your home. 
 And Tony DiTerlizzi's artwork is simply perfect for the story that he and Black are telling. Lots of intricate pen-and-ink drawings, depicting the pretty ethereal nature sprites, the weird multilensed "seeing stone," the drippy long-nosed troll, and spiky trees hung with cages. The highlights are an old newspaper clipping about a boy gone missing -- it seems to be important, though not yet clear. 
 Simon basically serves as a damsel in this book, but Jared's intense attachment to his twin is shown by him almost throttling Thimbletack to get the lens, and Mallory gets to kick goblin butt with her fencing sword. What's more, the kids' involvement in the world of the fey becomes more concrete when they gain a brand-new pet. Wonder how their mom will react. 
 The second chapter of the Spiderwick Chronicles, "The Seeing Stone," expands the eerie fey world into the more everyday one, and adds in some very nasty little creatures. It's sure to only get worse.