Don’t expect a sugar rush from “Charlie and the Chocolate Factory,” the new musical that opened at the Lunt-Fontanne Theater on Sunday. This latest adaptation of Roald Dahl’s winningly sinister children’s story from 1964 is — thank heaven — no sweeter than the two film adaptations it inspired, starring Gene Wilder (1971) and Johnny Depp (2005).

Then again, this big but tentative show — which features a book by David Greig and songs by Marc Shaiman and Scott Wittman — doesn’t burst with flavor of any kind, at least not during its exposition-crammed first act. Only in its second half does the show acquire a distinct taste, and it definitely isn’t confectionary.

That no one goes to Dahl for the blandly picturesque was made clear a few years ago by the success of the darkness-shrouded musical adaptation of his “Matilda.” The appeal of this writer, for both children and grown-ups, has always been his nasty streak.