I found this reads more like a memoir, (akin to Everything I Know About Love by Dolly Alderton, especially.) and not a work of fiction. I’m not sure how autobiographical this story is but the structure seems awkward for a novel. If it was a memoir looking back at the authors life, I would be more inclined to ignore this books faults but there’s a lot that didn’t work for me. Firstly, the writing was elementary and lazy at times. Secondly, I had no real sense of who Leah was because any attempt at fleshing her out was too direct. Also the love story seemed impersonal, like it was told from a distance even when we as readers were in the middle of supposed heartwarming, love building moments. 
Most importantly, Charlie was reduced to simply & solely an addict. There were no attempts to give any context to his character or his fight for sobriety. The language around his addiction is outdated for a book that came out so recently- referring to him as an addict instead of a person with an addiction. Leah blamed all her unhappiness on Charlie & his illness but never really took accountability for her flaws or how she aided in her own suffering. I’ve read my fair share of chaotic, depressed female characters but Leah did not have the same honesty or self awareness to make the story work. I don’t need a perfect ending, for the characters to make some huge life altering change in the way of self betterment but girl come on… go to therapy !!

if this is based on real life, rip Charlie. Hope you’re not hurting anymore