I am especially fond of book cosplay, which is perhaps why, though I rail against descriptions of mundane clothes in books - who cares how distressed your boyfriend's jeans are, YA heroine? - I love, love, love when a character's garb is unusual or symbolic in some way and the author takes some time to describe it in detail. Because these things make great costumes; specifically, great costumes I wish I had the time and resources to make, and the opportunity to squeal in delight when recognized at a con.
I've had a dream of cosplaying Sabriel from Garth Nix's Abhorsen trilogy for years and may yet, if I can connive a method of embroidering dozens of silver keys on a great swathe of surcoat fabric. And, you know, find seven bells of graduating sizes, because this cosplayer has not yet ventured into the realm of mold making, and probably should resist dumping money into yet another hobby.
What I love about Nix's descriptions isn't just that the clothes are beautiful, but that they have meaning in the world the characters occupy, that they're instantly recognizable, that their weight is both physical and figurative. I felt the same way when reading Leigh Bardugo's Grisha series, with the keftas. How freakin' cool are the keftas?! Likewise the stillsuits in Dune.
As a writer, I've had characters glancing in mirrors beaten out of me, so sneaking in the opportunity to dress somebody requires a bit of creativity. There was one passage, in particular, where I allowed myself to linger describing a garment that Eiren wears late in the book:
"Embroidered along the hood and sleeves were... detailed renderings, scenes and figures playing out the details of their lives.
But it was not any life, it was mine. My mother carried me as an infant from the birthing chair to my father’s arms, Jurnus and I raced through the streets and the sand. I bent my head in prayer, I burned ritual herbs, I braided Esbat’s hair and soothed Lista’s vanity. I went into exile with my parents, brother, and sisters. The figures were tiny and but a handful of knots each, but I recognized them all, and could see when Morainn and Gannet entered my life, crawling dark and glinting with gilded thread in the capitol tower.
We looked like figures of myth, all splashes of color and fine, spidery features. It was breathtaking, and I could hardly imagine wearing such a life for all I had lived it."
While I would never cosplay one of my own characters, it is perhaps a not-so-secret and ridiculously vain writerly hope of mine that somebody else someday might want to. I've got some very particular notions about Gannet's mask that defy description, if anyone's interested.