This book is very well written. If you like that kind of thing, and I do, you may want to read this book just for the prose. Maybe you'll have an issue with word choice occasionally or something like that, but overall, the writing is superb (characterization, narrative, dialogue, voice...). I was particularly impressed with how much suspense existed even though the story, for the most part, is simply depicting relationships between family members.
The story centers around a family, the Lamberts. Eventually you hop into the heads of every Lambert, at various ages. Most of the time the parents are elderly and the children are adults.
Some reviewers have written that none of those people are likable and I can see that. The book occasionally depressed me, but I did not dislike all the characters.
You can definitely find fault with all of them, that's for sure. If you need a hero, then this is probably not a book you'll enjoy.
The story is packed with meaning and insight. Others have cited a few digressions and talking turds, but I enjoyed a lot of it, most of it, whole chunks of it.
Such as... Chip, out of control, comically, sadly, disturbingly. Gary, depressed (hilariously built up over many pages). Gary's children and wife (all extremely distinct in my mind, as distinct as my own family). Gary and his siblings as children (different but so obviously the same people!). The descriptions of food when Denise became the focus (Mark Bittman Award). Enid's preoccupations. Alfred's competence at work. Sticking with Alfred. Depiction of dementia.
And much, much more.