Birdsong, Comedy Theatre, London<br/>The Big Fellah, Lyric Hammersmith, London

The dramatisation of a towering novel misses the mark, but an Icelandic invasion brings an infernal vision that is both alarming and entertaining

Listen hard and you might hear faint vibrations.

In one unforgettable chapter in Sebastian Faulks's acclaimed novel Birdsong, which hurls its protagonists into the horrors of the First World War, the Cockney Jack Firebrace is tunnelling under the Western Front. His unit's mission is to blow up the Hun's trenches, but the enemy are digging as well, intent on blasting the Brits to bits.

In that passage, Jack crouches, 40 feet down, his ear pressed into the mud, straining to hear if the Germans are mining alongside. Seconds later, exploding clay and rock hurtle past him, and, left rolling at his feet, is part of his mate Turner's face, attached to a chunk of skull. The big screen could, with ease, match Faulks's close-up descriptions. But can a West End adaptation do it? Big ask. Dismal outcome.

Director Trevor Nunn's premiere needs both more imagination and more finesse. A backcloth with projected battlefield photographs wobbles in and out of focus while a cross-section of tunnel (hardly claustrophobic) is winched on for the chaps to do a bit of crawling around downstage. The nearest you get to carnage is Jack's bitterly disillusioned commander, Ben Barnes's Stephen, brandishing what might be a dead man's thumb, but which looked (from where I was sitting) like a chipolata.

As the war drags on, Lee Ross does find some poignancy as grief-stricken, salt-of-the-earth Jack. It's a beautifully naturalistic performance, talking with a candle stub between his teeth as he pats his pocket for matches. Alas, this doesn't prevent the letters, which he and his chums send home, from sounding bland when read aloud. The transition from page to stage does them no favours at all.

In fact, it's hard to believe how unharrowing this is, given the subject matter. R C Sherriff's vintage Great War drama, Journey's End, was a thousand times more heartrending, revived at this same theatre in 2004.

Whenever Barnes's highly strung Stephen becomes impassioned, the dialogue veers towards risible melodrama. In the first part of Faulks's saga, set in pre-war Amiens, Stephen's supposedly torrid affair with Genevieve O'Reilly's Mrs Azaire is toe-curling – with faux-orgasmic, offstage cries ("Stephen!" "Isabelle!" "Yes!").

Nunn's relatively inexperienced adaptor, Rachel Wagstaff, engineers a few dramatic surprises, but the storyline mostly feels at once rushed and, at over three hours, interminable. Listen hard and you could almost hear the frustration, half the audience thinking: "If only I could burrow my way out of this one."

IRA paramilitaries are packing explosives into teddy bears in The Big Fellah. Spanning the years 1972 to 2001, Richard Bean's new drama tracks the history of the Troubles from an intriguing angle. He focuses on the underground support provided by certain Irish-Americans to Irish Republican terrorism. He has the action unfold in a shabby Bronx apartment. This is a safe house and local IRA HQ run by Finbar Lynch's David Costello – a softly spoken but icy Mafia type.

The Big Fellah should also be enthralling given its quota of dark humour, undercover agents, internecine rivalries and courts martial. Yet, strangely, the end result is a damp squib, in spite of fine ensemble playing from Rory Keenan, Claire Rafferty and others in Max Stafford-Clark's touring production (for Out of Joint).

The piece is politically informed but with obtrusive expositional facts. One might also wish Bean didn't stop at 9/11, given today's resurfacing tensions in Northern Ireland. He's clearly fascinated by the complexities of nationalism, but doesn't seem to sympathise deeply with any of his characters. Not Bean at his impressive best.

At one point, Costello says enlisting is like a Faustian pact with the devil, only you're signing up to a lifetime of pain. Well, in Goethe's Faust – pared down and radically adapted, in English, by the Icelandic troupe Vesturport – the antihero's desires seem pretty modest. Actor-turned-director Gisli Orn Gardarsson chooses (not for the first time) an OAP home as his setting. Johann is an aged thesp who's taken with a sweet nurse, Greta, for whom he recites snippets of Goethe's classic. That night, decrepit fellow residents and white-coated carers morph into devils. Hilmir Snaer Gudnason's punky Mephisto lurches around like a snarling bear crossed with a flopping corpse, sardonically helping Johann rejuvenate himself so he can seduce Greta.

Gardarsson's vision has some rough edges, but the creative chaos is wondrously dreamlike and playful – including a surreal disco routine in wheelchairs. Haunting fragments of poetry combine with thrilling aerial athletics. Demons bomb down from the rafters, landing in a black, bouncy net stretched over the audience. Scuttling like giant spiders above your head, and screeching infernally, they never quite drown out the music of the spheres (heavenly score by Nick Cave and Warren Ellis). Inspired.

'Birdsong' (0844 871 2118) booking to 15 Jan; 'The Big Fellah' (0871 221 1722) touring to 13 Nov; 'Faust' (020-7922 2922) to 30 Oct

Next Week:

Kate Bassett sees double as Rory Kinnear at the NT and John Simm at Sheffield's Crucible take on Hamlet