I can understand why many readers have struggled with this novel - The publication reviews are too extravagant, the structure of the novel is unconventional and the language is precise and restrained. Yes, it's one of those novels which requires its readers to put some effort into the act of reading and if that's not your thing (which is fine, by the way) you won't enjoy this work. But for me personally, I loved it.
No plot spoilers here but if you want to know what the book's about, it's about changing English attitudes to class and homosexuality over around a hundred years. In a sense it's a "country house novel" but Brideshead gets revisited once every twenty years or so. There's no single character viewpoint and one of the novel's pleasures (or frustrations, depending on your PoV) is working out at the beginning of each section who is speaking and what their relationship is to the characters and events previously established. There's no single plot strand or resolution because the central theme is the changing nature of memory and the tension between remembering and living ie creating new memories. "The Stranger's Child" represents metaphorically and literally the descendant who comes after us, caring for and knowing nothing of our own lives.
And the language can at times be quite beautiful. I've been marveling for days over the following which sums up a character, an age, a life in a few lines. "On a plate with a doily were five biscuits... he was touched for a moment by a sense of the inseparable poverty and consistency of English life, as crystallized in the Peek Frean assortment box." Echoes of T S Eliot, "I have measured out my life in coffee spoons".