An early fixup The Voyage of the Space Beagle (1950) by A. E. van Vogt

The Voyage of the Space Beagle (1950) is a science fiction novel by Canadian-American writer A. E. van Vogt. An example of space opera subgenre, the novel is a "fix-up" compilation of four previously published stories. Wikipedia

In the early part of the twentieth century, science fiction was published almost entirely in low-paying pulp magazines. The pulps mostly published short stories. Book publishers say that nobody buys short stories; they only want novels. So authors such as A. E. Van Vogt would write and sell short stories with recurring settings and characters and then sell them to book publishers as novels. Van Vogt coined the term “fixup” for such novels, and his book The Voyage of the Space Beagle (1950) was one of the first.

To quote the Wikipedia, it was put together from four previously-published stories:

1. "Black Destroyer" (cover story of the July, 1939, issue of Astounding magazine—the first published SF by A. E. van Vogt) (chapters 1 to 6)
2. "War of Nerves" (May, 1950, Other Worlds magazine) (chapters 9 to 12)
3. "Discord in Scarlet" (cover story of the December, 1939, issue of Astounding magazine—the second published SF by A. E. van Vogt) (chapters 13 to 21)
4. "M33 in Andromeda" (August, 1943, Astounding magazine, later published as a story in the book M33 in Andromeda (1971)) (chapters 22 to 28) Hardcover original First paperback edition

Other fixups