I saw this for the second time a few days ago at the Silent Theater, here in Los Angeles. I'm a relative latecomer to Francois Truffaut - I didn't see any of his movies until about five or six years ago, but was instantly hooked.
Of the Truffaut movies that I've seen, Adele H. is one of my absolute favorites - for one thing, I'm a fan of the 'person goes crazy' subgenre of movies. It's a personal film about pure obsession, depicted as something irrational but compelling, tragic yet unavoidable, and Isabelle Adjani is outstanding as the doomed daughter of Victor Hugo who becomes obsessed with a British Army officer beyond all reason.
One thought I had in watching it this time around, though, was spurred by a recent New Yorker article on the writer Ian McEwan, who is quoted as saying that he wrote his novel Enduring Love as an argument against the romanticization of irrationality (it's a novel about an irrational, romantically motivated stalker taking on a very rational everyman). So while Adele H. definitely shows that the poor woman is destroyed by her obsession, it also oozes with doomed romanticism. Now don't get me wrong, Truffaut's achievement is expertly made and highly seductive - but it also strikes me as just a teensy, tiny bit false to make a romantic movie about what is, ultimately, a person suffering from mental illness.
Don't take this as much more than a quibble, though, because I like the film very much as a cathartic, emotional experience. But I also think that it doesn't hold up to intellectual scrutiny as much as, say, The 400 Blows does.