Yes, this sounds like a strange book, and indeed it is, although I'm sure that all of Lapeyre's books must be: in the three I've read so far, waiting is the main theme. But this is not Waiting for Godot, and is in many ways unlike the work of Samuel Beckett, things do end. And Lapeyre seems to be so preoccupied with the nature of waiting that it could be said that he seems to be devising a taxonomy of the subject: in La Vie est brève et le désir sans fin there was a brief mention of waiting as a religion, although if religion is supposed to represent a (surely dubious) variety of freedom it becomes a form of error, of enslavement in L'Homme-sœur, in which Cooper becomes a prisoner of his own mind. Much as I loathe translation, I'll try to give an English interpretation of the French in an attempt to convey the sense of one paragraph of this:
'Cooper can very well imagine himself on the platform of a station that's been disused for years, calmly waiting for the woman of his life. That would be typical of him. Perhaps he would be surprised by the state of the station, would reflect on the delay of the trains and on the lack of consideration given to travelers; but it wouldn't cross his mind that he'd got the wrong station, nor of course that he'd got the wrong life.'
Cooper isn't a pathetic forty-year-old male virgin: he's lived (admittedly for very short periods) with three women, he's (with little success) tried prostitutes, and he's even nurtured hopes about the much younger Robine, the friend of his sister who would perhaps have brought him closer to Louise, even have been a substitute for her. But it is not to be. Nicole, the fortyish virgin ex-work colleague is only too ready to help him, even move in with him in a, er, sisterly way, but nor is that to be. So he just becomes his sister, in a virtual kind of way.
My other posts on Patrick Lapeyre:
Patrick Lapeyre: La vie est brève et le désir sans fin