Transit, By Bernard Share

In the toilets of a Gulf state airport in the 1990s, one dog-tired Irish globe-trotter pees on another's shoe ("a stream of near-unconsciousness"). Soon enough, these two ageing Africa hands (development-aid bigwigs, we deduce) have nosed out a shared history over a challenging bottle of Jordanian red. Back in the gents, they find that a mysterious door leads not into a cleaner's cupboard but a country boozer in the Ireland of their joint youth, c1949. A repeat visit flushes them back to 1950 and Trinity College Dublin, that crumbling "fortress of the Ascendancy" where both studied at that period.

Cue a deliciously sly and offbeat novel of time-travel, scrambled pasts, abandoned hopes and Ireland, old and new. If Samuel Beckett ever returned to write a Doctor Who special, it might closely resemble Transit.

The prolific novelist and historian Bernard Share, a TCD alumnus of a slightly later vintage, achieves much more than a whimsical homage to the Irish greats whose words and ideas flit through this slender but pregnant novel. He adopts the gimmick of some Hollywood high-concept movie: revisit the scenes of your college days, and even shed that "sixty-year-old tub of guts" to inhabit your younger, fitter self. From this device he fashions a droll and touching comedy that, paranormal machinery aside, exposes the unhealed wounds of memory, nostalgia and regret. "The past," our time-warp trippers soon grasp, "is not all it's cracked up to be."

In lissom, cat-like sentences, rippling with allusion but shorn of platitude, Share makes merry with the dank and tweedy, early-closing Dublin of the age. Beadily observed by the pigeon-obsessed bus driver Mr O (Flann O'Brien, take a bow), the two rejuvenated undergrads slip back into the world of tea-time invitations to young ladies in college digs (permission of the Junior Dean compulsory), against-the-clock boozing in back bars and sexual frustrations as steamed-up as the fuggy air on those licensed premises. "Rimmer" must once again pursue the cami-knickered Miss Cameron and then fall for the addictive – and addicted – Barbara, wild and waiting in her Ballsbridge flat.

As he glances sharply at the tropes of time-travel fiction (can our pair fix the past and so upgrade their present?), Share also spans the abyss between two Irelands. Even from this Nineties vantage-point, the tight-laced nation has already travelled fast and far, pioneering "all the strategems in the move from mountain farm to Mercedes".

As surreal jolts send us, lavatory portal by lavatory portal, from a student staging of Hamlet (a nod to Joyce's Ulysses) to a VIP latrine in Kenya, the past forfeits its glamour and Rimmer suspects that "hindsight is overrated". "Stranger in a strange land", he comes to know that – whether you hang a sign marked Irish humour, metaphysics or fantasy on this capacious cubicle of fiction - he can't go home again.