For a modern children's fantasy, in all its derivative glory, I really enjoyed this. It's not blazing any new ground, and it uses more than a few fantasy cliches (Henry's an orphan! taken in by his aunt and uncle! And his makeshift attic bedroom holds SECRETS! A locked door downstairs! An old man Henry can't remember! Cupboards that go to OTHER WORLDS!) but it still manages to feel fresh and fun. It helps that we're more than halfway through the book before anyone goes through any of the cupboards, and we never really explore the other worlds. Somehow that makes it better for me. 
 My biggest complaint about this book is that it is, according to the back cover, "the first book of a new fantasy adventure." I finished the last chapter and was thinking about how nice it was to read a stand-alone fantasy for a change, and then there was an epilogue, to set up the villain for the next book. I preferred the ambiguity.