When mystery author Sue Grafton died at the end of December, she famously left her Alphabet Series of mysteries unfinished. The summer of 2017 saw the publication of the penultimate volume in the series — Y Is for Yesterday — and Grafton hadn’t even started writing Z Is for Zero, which she had always referred to as her final book. When announcing Grafton’s death, her daughter wrote that the series will remain unfinished: “As far as we in the family are concerned, the alphabet now ends at Y.”

Nobody knows exactly what Grafton had planned for Z Is for Zero, but the disappearance of Zero doesn’t retroactively detract from the rest of the series. The Alphabet Series followed the adventures of private detective Kinsey Millhone, but there wasn’t an overarching master-plot running through the series. Until this week I had never read any of Grafton’s books, but I admired the fact that she worked mightily to make sure that any new reader could pick up any Alphabet mystery and get a complete story in one volume. While Millhone changed and grew and remembered the events that happened in past volumes, each book could be read as a standalone story.

Series-crazed genre publishers of today would do well to learn from this philosophy. Most series lose readers as they progress, while Grafton’s Alphabet Series seemingly gained thousands of readers with each new volume. She understood that every book deserves a real ending, and that fans don’t need to be coaxed into returning through some absurd series of cliffhangers. What series readers want is a compelling character, written well. And every available metric — popularity, longevity, awards — indicates that Grafton was one of the most successful series authors of our time.

I'm not exactly sure why I had never read an Alphabet Series novel. There are a lot of reasons, and they're all pretty bad. When I was in my teens and early twenties, I snobbishly considered all mystery series to be the province of old ladies, and not serious-minded, anti-corporate angry young men like me. And then I discovered Patricia Highsmith’s Ripley novels, and Jim Thompson’s journeys into psychological hell. Those thrillers urged me into the mystery section, and over the years I’ve fallen in love with plenty of mystery series by authors like Rex Stout and Kinky Friedman and Laurie King and Agatha Christie and Walter Mosley.

It’s possible that Grafton's books were so ubiquitous — all the different decades’ worth of mass markets in several different styles of trade dress, lining the shelves at used bookshops and thrift stores like wallpaper — that I never noticed them. They were always available in great quantity and so I didn’t give them a second thought.

But when I read about Grafton’s death, and saw her fans pay tribute on Twitter, I realized I’d made a mistake. This was a series that spanned nearly my entire lifetime — including well over a decade working in bookstores — and I only had the vaguest experience with it. It felt wrong, like I’d been doing Grafton (and maybe myself) a disservice. So over a New Year’s trip to Whidbey Island, on a visit to the South Whidbey Commons coffee shop and bookstore, I scooped up a battered copy of D Is for Deadbeat from the $1 cart next to the cash register. I read it in two big gulps — the first half on the last day of 2017, and the second half on the first day of 2018.

When I chose Deadbeat, I left several other Grafton books behind, including M Is for Malice and U Is for Undertow. Why, out of all the alphabet soup sitting on the rack at the Commons, did I pick D Is for Deadbeat? A quick internet search while waiting for my coffee revealed that it’s commonly considered one of the best Grafton mysteries; most of the fan rankings online place it firmly in the top five.

But also, Deadbeat was the earliest book in the series available in the shop. In the decades that Grafton wrote about Kinsey Millhone, the series gradually shifted from contemporary thrillers to period pieces. A Is for Alibi was published in (and is set in) 1982; V Is for Vengeance was published in 2011, but it takes place in 1988. Deadbeat was published in 1987, at which point Grafton had probably already realized that she was aging faster than her protagonist. It seems to mark a significant shift in the relationship between the writer and her work — the point when she stepped outside Millhone’s world and observed it as something different from her own.

Deadbeat begins with a standard detective-novel plot: Millhone is hired by a distasteful man — one who gives off the air of being a “derelict” — to deliver a large check to a young man. He explains to Millhone, the situation is “sort of like that Charles Dickens book, Great Expectations. He might not like having a convicted felon for a benefactor. People have strange ideas about ex-cons.”

Not too much later, the unsavory man turns up dead. He stiffs Millhone on the bill, and she, perturbed, sets off to figure out what’s going on. Deadbeat follows a pretty standard mystery plot. Millhone interviews a number of people, stakes out some suspicious characters, and slowly pieces together the dead man’s story. The structure of the book is sturdy and the reader makes realizations at about the same pace as Millhone, which is a difficult trick to pull off.

But while the plot is more than compelling enough to keep you turning pages, Grafton’s knack for character is what propels this story. Millhone is a dazzling narrator. She reminds us three times in the first couple dozen pages that she’s a liar, which sets the reader on edge, and then she proceeds to charm us into believing her.

It’s Millhone’s rough edges that make her so likable. In her search for answers, she encounters a customer service representative who is decidedly unhelpful. Millhone loses her temper.

I stared down at the desk. When I was in kindergarten, I was a biter and I still struggle with the urge. It just feels good, you know? “I want to speak to your supervisor.”

Elsewhere, Millhone watches a family member observing a corpse in a funeral home: “I don’t know why people stand and study the dead that way. It makes about as much sense as paying homage to the cardboard box your favorite shoes once came in.” She’s a misanthrope, but cheerfully so, and just funny enough that you want to keep listening.

Millhone’s not the only personality in this book, though. One of the best parts of Deadbeat is the fact that every person Millhone interviews has something else going on. One witness keeps trying to sell Millhone some pot. Another man spends his entire interview with Millhone whittling at a bar of soap with a knife. In the end of their talk, she notices what he’s been doing:

It looked like he’d carved a sow lying on her side with a litter of piglets scrambling over her to nurse. The whole of it couldn’t have been more than four inches long.

It’s not a detail that moves the plot forward at all, but it’s a surprising image that bestows upon the whittler a vivid interior life. When even the bit players in the book have distinct personalities, it makes the major points — the murder, the cover-up, the motivations — feel richer. The stakes feel higher. You can hear the pulses of every human in the book.

Grafton does spin out a few clunkers. For instance, it’s hard to imagine the Millhone who reflects fondly back on her young days of biting fellow kindergarteners also saying this line: “I drank in the heady perfume of the sea, watching the restless surge of the waves….” But those flat notes are rare, and they are brief. Deadbeat is on the whole superbly crafted.

Without revealing what happens, the climax of Deadbeat took me by surprise with its aching humanity. Millhone, who’s spent much of the book expecting the worst from her fellow humans and being richly rewarded for those negative expectations, demonstrates that her spiky shell is only a millimeter or two thick. Underneath her barbs and sharp knuckles, she’s a detective with a weighty sense of honor. For someone who equates a dead body with a cardboard box, she’s awfully concerned with honoring the dead, with seeing justice done in their names.

Assuming Grafton’s estate continues to respect the author’s wishes, there will be no Alphabet Series TV or movie adaptations. No other writers will ever publish the continuing adventures of Millhone. This is a very good thing. Grafton understood that the finite nature of Millhone’s existence is a strength. The fact that any reader can back into her world through any one of her books means that Millhone will keep collecting fans for decades to come, and those readers will likely want to immerse themselves in every detail of her world, to understand the character’s journey from top to bottom, from beginning to end and back again, from A to — well — to almost Z.