This was one of those books that nearly made me throw my Kindle at the wall! The level of assholery on Aston's part was way beyond what I am usually prepared to accept.
He is a complete bastard to just about everyone for years;
And when he and Glen got together twenty years later and the past was brought up - a past which had hurt Glen deeply - Aston's reaction was
"It's been twenty years, Glen. Bloody long time to hold a grudge."
It took ages for Aston to even apologize and then Glen jumped right in eager to take some of the blame for their relationship failing in the past. I hated that! Let the man grovel. He was the jerk, not you.
The ending was predictable; there was really only one kind of gesture Aston could make to fix things, and he did. But to me a typical too little too late.