Parallel follows Karl in a dual timeline: just after WWII in a divided Germany, starting his parallel lives (marriage, kids VS being gay when it is a crime), and in his first months of retirement, in the 80s (fairly alone, estranged from his daughter). 
This is a very sad story. It is a story of a gay man in a time and place where it was illegal to be. There is a flicker of joy here and there and it ends in a more or less uplifting note, but overall it's quite depressing.  The characters are not loveable (except for one side character or two), they are complex and do as much bad stuff as they do good. But this makes it quite an unusual story to read. If you are looking for something to warm your heart I don't think this one is right for you. This one if for those that want an unusual queer tale from an unusual historical place and perspective.
The art style is quite monochrome and stark throughout, the colorfulness of the left side of the cover isn't present. 
Overall, this one wasn't outstanding for me - something never quite clicked correctly, but it was an interesting read.
TW: Homophobia (by individuals and police), outing, suicide of a side character

I voluntarily read and reviewed an advanced copy of this book. All thoughts and opinions are my own. Thank you to NetGalley and OniPress for this opportunity.