You are a specialist in old books,
hired to look into a mysterious tome rumoured to be co-authored by Satan.
Suspicious deaths and mysteriously-powered babe Seigneur start
dogging your every move in roughly equal proportions. At what point do you
say "Sod this for a game of soldiers", hand said book back to its owner (Langella) and
return to parting widows from their first editions of Don Quixote?
If you're Depp, you plough on, well
beyond the point at which any sensible individual would realise they were
inhabiting a Dennis Wheatley novel. Such qualms aside - somewhat addressed
through Depp's initially unlikeable persona - this is nice, spooky horror
of pleasing intelligence, in contrast to many recent genre entries. Depp
whizzes round Europe, trying to find which of the three copies is legit --
gotta catch 'em all, Johnny... If the ending would benefit from further
explanation (or, indeed, any explanation at all), it doesn't really matter:
the journey is the thing here, and that's entirely competent.