Back when I started as a writer, here was a common path in F&SF: You did short stories and then moved up to novels when you had -- supposedly -- an audience. You didn't need an agent for stories you could send to the 'zines, and you only went looking for one when you were ready to commit bookery in the first degree.
A dozen or so sold stories along, I went to a convention and ran into a writer/artist I knew. He had an agent; she had just quit the big agency for whom she worked to go out on her own, and if I was looking for representation, I probably had enough credits -- if I was ready to do novels.
I didn't know if I was or not, but when I got home, I fired off a letter to the lady, listed my credits, and allowed as how I was ready to write a book that I had in mind.
Fine, she said, send me three chapters and an outline.
Well, shit. I didn't have a book in mind. Also, I didn't know from outlines. I had never written anything longer than five or ten thousand words. I could cobble together three chapters, but how would I know what was gonna be in the outline if I didn't know how the book was going to end?
So I hastily sat down and wrote the novel, a kinda SF, kinda fantasy thing called Seek the Magician. It was based largely upon a tarot spread I cast, having learned how to do that. With manuscript for a book in hand, I then wrote an outline, probably ten or twelve pages, based on the draft, bundled it up with the first three chapters, and sent it off.
The agent liked the chapters and outline. Send me the rest, she said. I did. She agreed to represent me.
Hooray! I had an agent.
I went on to my next book, which was a good thing, because after a year or so of trying, she was unable to sell the first one. Fell between two stools, so the rejections went -- too much fantasy for this editor; too much science fiction for that one. It was a long post-apoc world with magic, but there were still satellites that had somehow managed to stay in orbit.
Bad notion at the time. Didn't slot neatly.
Meanwhile, the second book, The Tularemia Gambit, finished about 1980 or so, went in, and eventually, found a home. So while it was the second novel I wrote, it was the first to be published.
The first novel I wrote? Well, it went into a drawer, and I figured it would never see the light of day. Lot of writers have those, the books they learned upon, and some of them leave instructions that if they die suddenly, somebody should burn it.
But until they die, they keep it. Why? Well, as I pointed out in the previous essay, because you never know.
A few years later, I had sold several books, and got as a result, a gig writing a couple of Conan™ novels. Eventually, that turned into five of those, and remembering my first stillborn literary child, I disinterred it, scraped off the mold, and after changing names and doing some relatively small revisions, built one of the Conan novels around it. I estimate I was able to use somewhere around sixty percent of Seek, maybe a bit more, and it not only saved me a lot of work, it fit the part pretty well. Whole chunks of it got transplanted with just the smallest of trims.
Kind of like being an organ donor and having your heart or lungs or eyes live on in a new body.
There's another reason why you never throw anything you write away. It was the first time, but it wasn't the last that I had a spare part when I needed one.