I've read quite a few of Douglas Coupland's books, but this one has been sitting on my shelf in hardcover since it first came out (nearly ten years ago now). While I consider myself a Coupland fan, I prefer his more lighthearted work and can only take his heavier pen in small doses. Eleanor Rigby is heavy subject matter (the book's primary theme is loneliness), but it carries itself in a surprisingly cheerful and optimistic tone. While this makes the book easier to read and enjoy, it's also my main criticism. I could clearly relate to Coupland's protagonist, having faced crippling issues with loneliness in the past, and had I read the book at that point in my life, the "happily ever after" attitude of the narrative would have felt false, shallow, and borderline insulting.
As for eccentric mothers, this book contains two. The protagonist's mother is eccentric in that she's realistic. She has quirks and annoyances that drive her children mad (criticizing their appearances, unintentionally pitting them against one another, etc). She's a minor character, but she's painted so well that you're pretty sure this woman is based on a real person. The second is the protagonist herself - a lonely, overweight, middle-aged woman who had happened to unwittingly end up pregnant as a teenager. The catalyst of the plot is the appearance of her adult son in her otherwise-empty life and the process through which she learns to open herself up and accept other people into her life. Being thrust suddenly into motherhood so late in life, she's clearly not a run-of-the-mill mother, though she takes to the role with apparent ease.