The End of the Affair is a strange book, it doesn't at any point make you want to cheer for Bendrix and Sarah, the two lovers who are kept apart by her marriage and his jealousy and obsession.
To be honest you feel empty and void at the end of the book, just like Bendrix does, and he is pretty miserable throughout due to his obsession with Sarah, the only person he seems to be truly human with.
The book is loosely based on Greene's own affairs, the key scene in the book, the bombing is based on his house. The End of the Affair is also openly questioning religion, and loving God vs believing in him, along with the other themes of jealousy and obsession.
However in my personal opinion the characters seem too flawed and you cannot feel anything for them. Sarah though she is in love with Bendrix, has a strange fixation with destiny and letting God decide.
Is this weakness or blind faith? I'm not sure because she stuck with her husband who was a total bore, but she wasn't brave enough to leave him for Bendrix the man she loved because she was so uncertain about religion.
This conflict of interests didn't make me stand up for her. I can't defend her because in the end she appears, even her escape (a euphemism to avoid spoilers) seemed weak also. Greene creates Sarah Miles as a woman who is in a catch-22 situation, she's damned if she does and she's damned if she doesn't.
Bendrix doesn't believe in anything, not love, not God and in the end he hates both even more. He started the book believing his affair would end quicker than it started, Sarah was the extreme opposite and it is this contrast which gets you through the book, you want to see who is right, and you may be surprised by the ending.