Searching for this book

[LEET]

Hi all, my first post.

 

I have been searching for this novel for over 30 years & still no luck.

 

It's a tricky one because i don't know the author or the title, just the general premise of what i remember. It's a novel about a hit man but with a twist, a really super twist.

 

I read the book around 1990 & it was a little tattered at this point so is probably from the 60's or 70's, though could be the 80's.

 

The book begins with a guy in his youth & one scene i remember early on (& i could even have this wrong being 30 odd years)  is this person setting up shop in his neighbours loft to watch the family live their lives because his life was of little interest at the time, a bit dark i know. He would watch them for days on end.

 

As the book progresses there are 2 main characters,  a hit man & another person winding their way through this novel living separate lives at different time periods. It's a fascinating read but won't spoil the outcome in case someone else wants to read it.

 

I have little else to go on, not even a book cover & i know it's a long shot but thought someone might have an inkling as to what the novel is called or even an author who may written such a novel.

 

Thanks.