British author J.K. Rowling has conjured up her Harry Potter magic in the spin-off film Fantastic Beasts and Where to Find Them, but some early reviews wondered if it may be too dark for a family audience and whether the story can sustain four more movies.

The Warner Bros movie, to be released worldwide on Friday, got mixed reviews, with critics in Britain generally proving more enthusiastic than their US counterparts.

“That entertainment enchanter J.K. Rowling has come storming back to the world of magic in a shower of supernatural sparks and created a glorious fantasy-romance adventure,” wrote Peter Bradshaw in Britain’s Guardian newspaper.

Fantastic Beasts and Where to Find Them takes place 70 years before the first Harry Potter books and features a cast of new characters with magical powers. Set in 1926, it centres on Newt Scamander, a ‘magizoologist’ who arrives in New York with a case full of strange creatures that quickly escape.

It marks Rowling’s debut as a screenplay writer and is the first of five movies based on the Scamander character that seek to build on a wizarding franchise that has made $7 billion at the global box office.

The Hollywood Reporter’s John DeFore said Fantastic Beasts would appeal both to Potter fans and to newcomers, praising its invention and special effects. He wrote: “This world invites us in as effectively as the best of the Potter episodes.”

But DeFore said casual audiences “may be less convinced that this spin-off demands the five feature-length instalments Warner and Rowling have planned”.

Variety noted the film’s themes of intolerance and xenophobia beneath the wands and the cute beasts.

“Just when you thought the world of Harry Potter couldn’t get any darker, along comes a bleak-as-soot spin-off that makes the earlier series look like kids’ stuff,” wrote Variety’s Peter DeBruge.

Britain’s Telegraph, however, welcomed the bleak undercurrent, saying the film’s vision of Depression-era America “caught in the jaws of fear and paranoia has the stony-grim ring of the here and now”.

Others were less impressed. Entertainment Weekly’s Chris Nashawaty called the film “oddly lifeless.”

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