Memoirs aren't something I read a lot about, but this is one my mum had recommended to me ages ago, so I finally decided to pick it up. I recognised both Vita Sackville-West and Harold Nicolson's names, but I knew next to nothing about their writing, or who they were. Portrait of a Marriage is composed of several parts, some of which being written by Vita herself relatively early on in their marriage, and others being written by their son, Nigel Nicolson, after both his parents death. 
I found Vita's parts read almost like a novel. Written when she was quite young, everything was incredibly dramatic, and at times either extremely depressing or extremely whimsical. Her accounts of her youth and her affair with Violet Trefusis are filled with wild proclamations of love and dramatic tales of her escapades. I found Vita very interesting, and I'm curious to try reading one of her novels.
Nigel's parts are more documentary in nature, but no less interesting. He shares additional insight on Vita's life based on letters from her and others, as well as various people's diary entries and news articles from the time. He portrays his parents relationship as a loving and caring, however extremely unconventional, marriage. I additionally really enjoyed hearing more about Harold in his accounts, as most of Vita's writing focuses on Violet, with Harold being a supporting character. In Nigel's accounts, Harold is shown to be a brilliant and caring man who supported Vita despite her many quirks, and meanwhile was instrumental in global politics of the time. 
I also found the latter part of the book, where Nigel discusses their relationship after the affair, fascinating. Their relationship sounds like something to be aspired to, with trust and forgiveness being key in their relationship. Their later life, in their house and gardens filled with beautiful writing and peaceful solitude, sounds lovely.