When we talk about other people, my friend Leah and I divide them into two categories: some people are drains, and some are radiators. We do not think, of course, that anyone can be one thing for all people, and we do not assume, of course, total innocence, recognizing that we have been drains ourselves in our most unattractive moments. This method is as helpful as it is limited. But it has become useful shorthand for describing how someone is making us feel.

We agreed upon this terminology after Leah sent me Milton Glaser’s list of lessons he has learned over his decades-long career. The third lesson is that some people are toxic and you should avoid them; this idea goes hand in hand with the first lesson, which is that you can only work for people you like. Both seem easier said than implemented. Luckily there is a test you can perform to figure out the level of toxicity in your relationship with another person. Glaser explains:

You have spent some time with this person. Either you have a drink or go for dinner or you go to a ball game. It doesn’t matter very much, but at the end of that time you observe whether you are more energized or less energized. Whether you are tired or whether you are exhilarated. If you are more tired, then you have been poisoned. If you have more energy, you have been nourished. The test is almost infallible and I suggest that you use it for the rest of your life.

I forgot that the drain-radiator dichotomy essentially came from Milton Glaser until I was reading Americanah by Chimamanda Ngozi Adichie, prompted by Leah’s recommendation. “Chimamanda knows her drains,” Leah said when I had reached a section with a character I started to loathe so much that I needed to talk through my hatred, to expel it. “When Shan walked into the room,” Chimamanda writes, “all the air disappeared.” Shan appears only a handful of times in the book, but she leaves her mark. She is a self-satisfied writer who holds an infuriating spell of charm over her brother Blaine, who is desperate for her approval. Both are American blacks; the main character Ifemelu is a Nigerian immigrant working out the differences between them all. At one point in the story, it is 2008, and Ifemelu tells Shan she should read Dreams from My Father, to be more engaged in Obama’s candidacy. “It would be good if someone read my book,” Shan replies.

Adichie’s sense of humor—blunt, mordant, and predicated on a lack of understanding—buoys a novel that seeks to cover everything. It’s a messy book, at times leaning on the obvious, but it’s neatly structured, spanning decades, covering scenes of groups you could call one word if you didn’t mind losing the nuance that Adichie often does so well to bring out. Nuance is a loaded word, particularly when Blaine, a professor at Yale, clashes with Ifemelu over her blog about being an African in America. “I don’t want to explain, I want to observe,” she says when he offers edits to her posts. “You’re being lazy,” he counters. Blaine prefers explaining, but seemingly only when he or someone he respects does it. He is passionate about activism, protest, and novels “written by young and youngish men and packed with things, a fascinating, confounding accumulation of brands and music and comic books and icons, with emotions skimmed over, and each sentence stylishly aware of its own stylishness.” Blaine does not argue with Shan, memorably full of hot air, when she proclaims Americans to be “very ideological about fiction.” She professes: “You read American fiction to learn about dysfunctional white folk doing things that are weird to normal white folks.” The allure of her claim lies in its comforting reduction of emotions and ideas. It pretends to be observation when ultimately it’s an explanation, an education, an imposition.

This imperative to educate, at the expense of feeling, is one of the more insightful parts of an already insightful book. Explanation requires not seeming angry, not seeming hurt, and, paradoxically, skimming over some truth. Adichie is illustrating an unavoidable tension between a constant awareness of your differences and a natural desire to exist without explaining yourself. It is not hard to see why Ifemelu returns to Nigeria, why she would want to put down roots in a city where she does not play the role of visitor. As necessary as leaving might be, it is also exhausting. As important and wonderful as language is, there is no substitute for the shorthand that exists when you do not have to explain yourself to another person.

Leah’s complaint about Americanah is its focus on romantic relationships. Ifemelu’s life does break down conveniently into boyfriends: white alpha male Curt, black alpha male Blaine, and the singular Obinze, who transcends type as her first and most honest love. But Ifemelu’s biggest period of growth is arguably when she is alone and depressed, when she cuts off all contact with Obinze because she cannot bring herself to share her messiness and what she is going through. She fails a person by not involving him, by not explaining or observing. And I suppose she learns from it, although it takes a while for this knowledge to show itself. She writes, she dates, she moves from city to city. She learns how to present herself.

When she finally tells Obinze why she cut him out, he doesn’t say much, just that he wishes she had told him before, and the failure’s significance dissipates. A new obstacle to their relationship appears, like obstacles do. They fight, they separate, they reunite. It’s all very romantic. Chimamanda not only know her drains; she knows her radiators, she knows her love stories.

Sure, the ending lacks a certain nuance. But there is sometimes nothing more comforting than tying things up neatly, feeling one way and not the other, and having it feel like a revelation, not an imposition. In the final scene, Obinze makes an impassioned speech about wanting to be with Ifemelu, and she just stares at him, even though he is saying what she wants to hear, and you feel as hesitant as she does. Naturally she feels a little hesitation now that she finally has something she wants. She has always hoped for certainty, and now she feels an abundance of it, so much of it that she has to pause before she tells Obinze to come in.

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