An Assembly Such as This is a novel by Pamela Aidan. It is the first book in a trilogy entitled Fitzwilliam Darcy, Gentleman. The second and third books in the series are titled Duty and Desire, and These Three Remain.
All three books are inspired by Jane Austen's popular novel, Pride and Prejudice. The series centers around the character Fitzwilliam Darcy, and explores the events of Pride and Prejudice and Darcy's developing relationship with Elizabeth Bennet from his viewpoint.
As Darcy, uncomfortable in his current surroundings, worries about his sister Georgiana (who is still vulnerable following an unpleasant encounter with his nemesis, George Wickham) and attempts to tolerate the unsubtle and unwelcome advances of Bingley's sister Caroline, he finds himself repeatedly thrown into Elizabeth's company, particularly when her sister Jane falls ill whilst visiting Netherfield and is forced to stay there whilst she recovers. As the two begin to cautiously interact, Darcy comes to admire her lively spirit, generous nature and confident refusal to be cowed by her social 'betters', whilst struggling with her apparent unsuitability as a wife; as well as being from a lower rung of the gentry without money or fine connections to speak of, she also possesses embarrassing and 'unfortunate' relations, including immature younger sisters and a tactless and ill-bred mother who hardly bothers to conceal her transparent desire to have Bingley and her oldest daughter married. Darcy, who is quite protective of the somewhat naive and easily-trusting Bingley, attempts to dissuade Bingley from entering into what he views as an unfortunate and hasty relationship with Jane Bennet whilst struggling with his own developing feelings for Elizabeth.
Eventually, after reading a pleasing letter from his sister, Darcy determines to explore his feelings for Elizabeth despite his misgivings, and resolves to both make amends for his earlier rudeness and attempt to charm Elizabeth during a ball that Bingley is holding for his country neighbours. Unfortunately, despite the subtle (and not entirely welcome) assistance he receives in this from his personal valet, Fletcher, fate has conspired against Darcy - his enemy Wickham has recently moved into the area, joined the local militia and become acquainted with Elizabeth. As such, when Darcy takes the opportunity of joining Elizabeth for a dance at the ball, Darcy is subject to extremely cold and unfriendly treatment from her, more than can be explained by his earlier tactlessness. He realizes that Wickham has managed to poison Elizabeth against him with false tales of their previous dealings, and that she (and others in the village) have become distant towards Darcy because of his perceived arrogance and by Wickham's charming nature and spiteful lies; too proud to set the record straight, however, Darcy refuses to defend himself. Worse, Bingley's unguarded behaviour towards Jane Bennet, her mother's tactless gloating and more examples of ill-breeding from her family strengthen Darcy's conviction that he must prevent his friend's potential ruin at all costs - by dissuading him from marrying Jane Bennet, from whom Darcy has not detected any hint of regard for his friend beyond the merely polite. Despite the fact that to do this would permanently alienate Elizabeth, Darcy resolves to act in what he sees as the best interests of his friend; the next day, as the Netherfield party return to London, Darcy sows the seeds of doubt in Bingley's mind about Jane's regard for him, convincing Bingley not to return to Netherfield and declare his intentions to Jane. The novel ends with Darcy resolving to harden his heart and forget about Elizabeth.