This was a doubling of the first book in the Children of Violence series. What was enjoyable and engaging over 300-some pages in book 1 became downright tedious through 670. As others have said, Lessing may have realized "this is it!" and just crammed the rest of her life/fictitious-similar-life into the final book. Without making conscious effort, my brain was editing out several pages at a time, sometimes even whole story arcs that would have removed about 15-20 pages of text, to create a more concise story.

If you want to look deep, deep into the minds of several people, their motivations, loves, etc, then pick this up. However, there is so much here that is written down that does not advance the narrative or introduce/explain something about the characters that even turn-of-the-20th-century Russian authors are looking at this and saying "that's a lot of words."