Conclusion and final warning... sorry, final thoughts...
As for the single player game, well, it's neither dire nor good. In fact, it's decidedly average with a heavy dose of frustration and half-arsed ideas. You'll spend a lot of time running around hunting for items that are, at best, illogically placed and more often than not only found after ten minutes of re-exploring previously covered ground. This is a kids' game for crying out loud! My eldest, admittedly not blessed with the greatest attention span in the universe, spent fifteen fruitless minutes hunting for a fuse whilst getting more and more frustrated and bored until she disappeared upstairs to sulk and play loud music all evening. Ah, what a happy family life.The youngest was soon frustrated by the puzzles that either demanded yet more hunting of already explored areas or by riddles and clues that made no sense whatsoever and were hardly helped by a clumsily implemented log book system that has the damn game and setup options as its first page every time you opened it. Sure, there were few side-quests and the combat was easy enough but she was soon bored and went back to Barbie.com on her PC.
So here's my advice. Go see the film, buy the books and let your kid's imagination run wild. But if you've got a couple of kids "spoiled" by games that properly implement two-player co-op, leave The Spiderwick Chronicles on the shelf unless you want to have 20 minutes of moaning, as one or other of your kids is left to watch the other one play. That the box states 2 players isn't technically wrong but I would say that it is, at the very least, somewhat misleading. Especially so given the stated 2 player co-op mode. The unwary would reasonably expect that to mean the whole game is playable as a 2 player co-op, which it just isn't.
And just in case you were wondering, as a single player game it's not bad, but I'll bring in my "reservations about films tie-ins" here, which once again proves itself to be correct. The Spiderwick Chronicles is formulaic, wholly unremarkable and fails to inspire or innovate in just about every area. Of course, it has created a new genre of "Games to buy your kids to make them hate you", which I guess is something it could be proud of. Cheers.
Note: No, I didn't get forget give an award, The Spiderwick Chronicles doesn't deserve one, as in my opinion it barely does what it says on the box.