Anyone who has seen the trailer for Cyrus would be forgiven for thinking it was a slapstick comedy along the lines of Stepbrothers and films by the Farrelly Brothers, such as Shallow Hal and Dumb And Dumber.

And this is not a bad thing, especially when you have the talented clown-faced John C Reilly playing one of the central characters.

However, while this certainly has some laugh-out-loud moments and fine comic acting, Cyrus is certainly not the kind of comedy, or even rom-com, it is promoted as.

Splashed across the top of the poster is a quote from Rolling Stone: “Outrageous, twisted fun. You'll be laughing till it hurts.”

And, after watching it, all I can say is that the reviewer must have walked out halfway through as Cyrus is definitely a film of two halves.

The story centres around divorced film editor John (John C Reilly) who has been stuck in a depressive rut for the past seven years since the end of his marriage. He is prompted to re-enter the dating scene by his ex-wife Jamie (Catherine Keener), who is anxious to move on with her life with her fiancé.

Jamie drags a reluctant John to a party where he behaves like a desperate demented loon and somehow, unconvincingly, attracts the attention of Molly (Marisa Tomei).

The couple quickly become smitten but Molly is hiding a big secret – her obese son Cyrus (Jonah Hill), who would give Oedipus a run for his money in the whole maternal fixation stakes.

John then discovers Cyrus and becomes involved in a war of attrition as he tries to sabotage the relationship in various hilarious ways – so far so Stepbrothers.

The first part will have you doubled up in cringy recognition as John makes an abject prat of himself in his seduction attempts while Cyrus is portrayed as an emotionally retarded simpleton, stuck in his teen years, abusing synthesisers and play-wrestling with mum.

And, as a comedy in the slapstick vein, it is right up there with the aforementioned films.

But then the film eases into the second part and the tone completely changes. John goes from immature desperado to a mature, sensible man in almost nano seconds.

And Cyrus morphs from comedy to tragedy in the same manner as some deep issues are delved into and the film becomes a drama about boundary issues in modern relationships.

The fact that John C Reilly and Jonah Hill are convincing with their multiple personalities is testament to their superb character acting.

Reilly exchanges his gurning Krusty the Clown imitation for the demeanor of a serious family man with ease, depicting every emotion in a deep, multi-layered performance.

And while Hill is used to playing the village idiot, he shows a far greater range as a conflicted, smothered young man trying to escape from the confines of his bad attitude.

Cyrus is a mature film with a confused outlook. It is also an enjoyable film though the tonal variations result in a rather uncomfortable shift in mood.

But then, Cyrus is trying to be something for everyone and mostly succeeds. Though fans of the Farrelly brothers might want to step outside halfway through.