The lyrics of the movie musical La La Land are alone enough to recommend a show. They were written by the composers of this show. And, like the film, the songs here have that wordy (in the best possible sense) quality but without being verbose. It is a virtue that is present throughout this multi-award winning musica populated by American high school students and their parents and composed by Benji Pasek and Justin Paul who are responsible for both the music and lyrics.

And yet the music — which won a Tony in New York — is both a strength and a weakness. The tone is set early on with the guitar-driven rhythms of Anybody Have A Map? in which the mother of this musical’s loner hero Evan Hansen, relates how she has no idea how to guide her son through his debilitating social awkwardness. His doctor’s advice is to write himself letter of self confidence-boosting encouragement. This turns into the cornerstone of Steven Levenson’s clever plot.

One of the letters relates how the only light in Evan’s life is fellow student Zoe. It accidentally ends up in the possession of her brother Connor, another teen racked with self doubt and anxiety who later commits suicide (off stage, thankfully) but whose parents assume was writing to Evan because the letter in his possession starts Dear Evan Hanson. Seeing the desperation in Connor’s mother to learn what her uncommunicative son might have been feeling, Evan pretends they were good friends, a white lie that snowballs into a massive deception.

With the help of his sarky friend Jared, Evan fakes e-mails to prove his friendship with Connor. And it is here that the show achieves a rare, perhaps unique, psychological complexity as Jared, Evan and their imagined version of the dead Conner collaborate on writing e-mails that conveys the feelings of the young and suicidal.

The moment also represents what might be described as the climax — though by no means the end — of Pasek and Paul’s score with the song Sincerely, Me during which sees the three teens — two living, one dead — throw themselves into a common cause. The effect of the song is to energise a show that hitherto reflects the mainly downbeat emotions of its adult and teenager characters. Evan, of course, has plenty reasons to feel pessimistic about life, as does Connor’s grieving family and Evan’s mother Heidi whose life is made no easier by being a single parent.

This is not to say that the show is depressing. But in the way that it is composed it does mean that most if the music reflects roughly the same place on the wide spectrum of human emotion. Or, to put it bluntly, it’s good but samey.

Rarely for a musical, the real strength here is in the drama generated by Levenson’s script. Almost the entire two and a half hours of Michael Greif’s slick production, is strung out with a sense of dread for the moment when Evan — who by now has become an international social media star —will be exposed as big liar.

In his West End debut,newcomer Sam Tutty plays the role superbly well. He movingly conveys the crushing awkwardness that goes with no self-confidence,but also the gathering, tentative strength of someone who emerges from the condition. Lucy Anderson (also making her West End debut) is excellent in the role of Zoe, Connor’s sister.

Yet musically I kept thinking about another show that reflects teenage angst — Spring Awakening (2006) which lyrically and melodically brilliantly charts the full gamut of emotions so deeply felt by young people on the brink of self-destruction.