Literally the only film I have seen this year is Carol Reed's adaptation of this novel, published in 1944. So my write-up of it is very much based on the differences with the film, of which three seemed to me pretty significant.
The first, which concerns me most in a way, is that where the setting of Reed's film is somewhat ambiguous, Green's book is absolutely firmly set in Belfast in 1944. The city centre streets are named - Royal Avenue, Dublin Road, Victoria Street; and the tram that in the film is heading up the Falls Road is going up the Shankill in the book. Green therefore also catches the sectarian picture a bit more than the film does (or could); the youths on the tram chant "No Surrender!" at the police, the two ladies who care briefly for the fugitive Johnny are respectable Protestants, which adds an extra poignancy.
Second is the book's structure - whereas the film continually cuts between Johnny and his various pursuers, in the book he is almost absent from the first half after his colleagues abandon him, so that by the time we reach the mid point we are wondering what on earth has happened to him. Since he is then reintroduced to us half-way through the book, Green can be pretty clear about the fact that Johnny is dying as soon as he reappears; in the film there is a bit more suspense on this matter.
Third of course is the nature of the drama, culminating in the ending. It is inevitable, of course, that Johnny will die. But Green has Agnes and Father Tom more complicit in the manner of his death - and redemption, according to the last paragraph - than Reed. Throughout, Green talks about souls, faith, belief, where Reed concentrates more on character and action.
Altogether, it makes for a convincing package. William Hartnell's character, Mr Fancy, is here the sinister Fencie, ten years older: difficult to choose between them or some of the other differences in characterisation. But basically, as so often, the film is very good but the book is even better.