A review by blondierocket
The Wrath of Mulgarath by Holly Black, Tony DiTerlizzi

The end of the Spiderwick Chronicles series. After rescuing their sister, the twins return home to find their mother missing and realize that their only way of survival is to face Mulgarath, retrieve the field guide and make nice with the elves.

I thought it was a very good send to the series, so now I can watch the movie and make my comparisons.