VAGUE SPOILERS FOR THE END OF THE SERIES.
The primary theme of “The Witcher”, the first story in The Last Wish collection, is the worthiness of the professional who does his job with integrity despite the corruption and vagaries of politics and the upper classes. Corollary to this is the argument that society is kept moving not by the flashiest among us, but those who do hard and difficult work regardless of thanks or lucrative remuneration. This is totally explicit in the text, for example, when Geralt says to Ostrit:
“It will be easier to remove Foltest from the throne if the striga frightens people even more? If the royal madness completely disgusts both magnates and common folk, am I right? I came here by way of Redania and Novigrad. There is much talk there that there are those in Wyzim [Vizima] who look to King Vizimir as their savior and true monarch. But I, Lord Ostrit, do not care about politics, or the successions to thrones, or revolutions in palaces. I am here to accomplish my task. Have you never heard of a sense of responsibility and plain honesty? About professional ethics?”(The Last Wish 27, 2019 First Hardcover Edition).
Earlier in the story Geralt is arrested after successfully and violently countering a xenophobic attack. The difficulty of living with integrity and basic human decency in a thoroughly corrupt society (or even universe) is a constant theme in The Witcher texts. It would not be inappropriate to compare Geralt to an exterminator or plumber crossed with an infantryman. He even notes, when recounting wading through shit to fight a zeugl in “A Shard of Ice” (referenced frequently in The Witcher 3: Wild Hunt) that he was made, through training and mutation, to be numbed to the dreadful vileness of his profession so that he could fulfill it without fear.
In “The Witcher” we see Geralt pursue his profession in the most thorough detail ever shown in the books, because the saga is not really about being a witcher so much as what it means to be a witcher when the profession is dying and one no longer believes in being one. Most of this is only established later in The Last Wish, and certain lore elements of “The Witcher”, including the demand for witchers itself, are flatly contradicted by later stories. This reflects the fact that Sapkowksi wrote the first story as a one-off at his son’s behest and gradually expanded the universe into a larger work due to reader demand.
One element of the story reflects the eventual thematic direction the series would take quite heavily. This is the doomed love affair between Adda and Foltest, along with its destruction by the jealousy of Ostrit and his curse. The plot details are not the point. What matters is that from the beginning, The Witcher is framed as a story about tits and swords but is more accurately described as a tragic romance. Geralt of Rivia, the most famous witcher of his age, whose life has been one long decline from boyish dreams of heroic valor, is destined to find all he seeks in life, and then lose it (at least in the texts. The games tell a happier story). Several times in the later novels he is called “anachronistic”, the superannuation of a sunken realm* in which the world was chivalrous, witchers were necessary, and evil acted in darkness with fangs and claws, not in the cold light of day “according to rights”, as Geralt says in The Lady of the Lake. The Witcher is not a Tolkienesque series on the whole, but it is in this one and crucial factor; namely, its obsession with the inexorable and tragic march of time.
No witcher’s ever died in his bed
The eponymous short story is a snapshot of Geralt at the exact point in which “business as usual”, or the life of an emotionally repressed and cynical workaholic, begins to end. Later stories established that “The Witcher ” follows “A Question of Price” (equivalent to S1E4 of the Netflix show) and “The Last Wish” (S1E5 equivalent). The show changed this, but it is retroactively important to the text. By the time he fought the striga in the crypts of Wyzim, Geralt had both loved and left Yennefer after a four year relationship and invoked and then ignored the Law of Surprise. Destiny, Nenneke suggests in the frame story “The Voice of Reason 2”, is wroth with Geralt, because he is telling Her to fuck off, and Destiny has no intention of doing so. Geralt is not the same. He is “slipping”. He has begun to see a life beyond witcher’s work, broing around with Jaskier, and the semi-frequent prostitute fling. Something more. Consequently, whether on account of powers invisible or his own psychology, he is getting worse at his job, and nearly dies fulfilling the contract. Life is not just “Monsters and money”. It never was, and now the fiction has become untenable. As a river flows down a mountainside to the sea, so will Geralt of Rivia become the “witcher-knight” he has always yearned to be. Either way, he is fated for violent death, and always has been. But what will he die for in the end, and live for in the interim?
Much of this can only be gleaned from the story in embryonic form or in juxtaposition with the rest of The Last Wish collection, but the fact that Sapkowski wrote the frame story “The Voice of Reason” to collect his first six witcher tales, each segment of which reflects upon its preceding tale originally published separately, indicates that the short stories are not merely episodic nor meant to be take in isolation. “The Witcher” is not a one-off; it’s the opening shot of the franchise and, when seen in the final context in which it was eventually canonized, establishes much of the subsequent tone and thematic concerns.
*paraphrased from John Keats’ The Fall of Hyperion: A Dream
**only after completing the article did I notice the questioner was referring to the whole series. Oh well.