When I was a teenager, I got Lord Foul’s Bane by Stephen R. Donaldson. It is about a leper who gets transported to a fantasy world that he thinks is all in his head, hence the unbeliever part of title for the series: The Chronicles of Thomas Covenant, the Unbeliever. Yes, this was a trilogy. At the time I received the gift, a second trilogy had already been released, and I bought all the books to read and enjoy.
I must admit, I haven’t reread, and I never quite got around to The Last Chronicles of Thomas Covenant, which I think is up to four books. Still, the original trilogy makes my books of influence list. The story is memorable, the writing is decent, and it was my introduction to series longer than three books. If you like a world or a character that an author creates, you can return again and again for new stories. At least until something else catches your interest.
Lord Foul’s Bane was probably one of the best gifts I’ve ever gotten. It has also been one of the costliest, if you factor in all the books I’ve bought in all the series I’ve read. The gift that keeps on costing money.