I stopped doing History at school before O levels as I wasn't particularly interested at that time in the First World War, which was a large part of the syllabus and I also preferred to do Music, which would have clashed on the timetable.
However, I was a voracious reader and my youngest aunt, who was only a few years older than me, used to pass on books that she thought I would enjoy. So I took the book 'Katherine', by Anya Seton with me on a holiday to Cornwall. It is the story of Katherine Swynford, the mistress of John of Gaunt who later became his wife, with their 4 children being legitimised on their marriage in 1396. The descendants of their eldest son, John Beaufort, Earl of Somerset, include Margaret Beaufort and her son Henry VII, founder of the Tudor dynasty.
John of Gaunt and Katherine Swynford also had one daughter, Joan. Her (2nd) marriage to Ralph Neville, Earl of Westmorland produced, among others, Cecily Neville, who was the mother of both Edward IV and Richard III. The rivalries between these two groups of cousins, led to the Wars of the Roses.
Meanwhile, John Beaufort's daughter, also Joan, married James I of Scotland, giving rise to the Stuart dynasty.
So, from a rather inauspicious start as the mistress of a king's third son, Katherine Swynford became the ancestor of every English, Scottish and British monarch in the last 600 years.
I spent that entire holiday with my head in that book and, although I never followed history at an academic level, I do credit 'Katherine' with sparking my interest in a subject which endures to this day.