Gripping and suspenseful, with echoes of other English classics like Jane Eyre. I'm actually surprised I've never read this before, besides the fact that I didn't know anything about it (unlike everyone else in the universe, apparently). I'm not the kind of fan that loves the moody broody heroes like Heathcliff and Rochester - their so-called "passion" sometimes ranges into the abusive and I find it in no way attractive. Mr. de Winter has hints of it in his character, but I found him a lot less violent and thus more sympathetic than similar leading men. This made it a lot easier to root for a happy ending.
The second Mrs. de Winter is sometimes criticized for being "spineless", but, like the moody hero, her character is a convention in the genre and I actually think it is done particularly well. She's a teenage girl, used to being dismissed, who's been thrust into a new role in a new world with a set of unfamiliar rules. I think du Maurier captures the voice of a self-doubting, self-absorbed, naïve and frightened adolescent very effectively. And while the feminist part of me cringes a little when the turning point of her identity development comes at the behest of a man, the romantic part of me (for whom I read these books in the first place) experiences her triumph with satisfaction.
This book is also memorable for many characters that create a visceral and emotional response with what seems like very little work. I haven't loathed anyone as much as Mrs. Danvers since I read David Copperfield.