ALEXANDER McCALL SMITH, I PRESUME: Tickets to “An Evening With Alexander McCall Smith” are $25-$35 ($15 for students). People willing to pay $75 for a ticket in order to support the Friends of the Princeton Public Library will receive the best seats (rows A-H). They will also receive a copy of the author’s latest book and attend a pre-show reception. Those willing to pay $50 a ticket will sit in a specially reserved section and receive a copy of the book.

There are prolific authors. And then there is Alexander McCall Smith. The Wikipedia website credits 75 titles to the extraordinarily productive writer, from The No. 1 Ladies’ Detective Agency, Sunday Philosophy Club, and 44 Scotland series to short stories, children’s books, and academic texts.

Mr. McCall Smith has fans all over the world. Among them is Princeton Theological Seminary president Iain Torrance, who also counts the author as a friend and even appears as a character in a few of his books. When Mr. McCall Smith comes to Princeton on Friday, April 20 to appear in “An Evening With Alexander McCall Smith” at McCarter Theatre, an event co-sponsored by the Friends of the Princeton Public Library, he will be staying with Mr. Torrance and his family.

“We were contemporaries at the University of Edinburgh in the sixties,” Mr. Torrance recalled last week. “He did philosophy of law and I did philosophy. We haven’t been constantly in correspondence, but we have known who the other is. I am always amused by him.”

Born in what is now known as Zimbabwe, Mr. McCall Smith was first published when he entered a literary competition while teaching at Queen’s University Belfast. His children’s book won first prize. He returned to southern Africa in 1981 to help co-found and teach law at the University of Botswana, which served as inspiration for numerous books to come.

“He has a great love of Africa. He taught law in Botswana at one stage and wrote a book on criminal law in Botswana,” Mr. Torrance said. “Out of that came his most famous series, The No. 1 Ladies Detective series. It has a very warm and wise understanding of contemporary Botswana. He has roots there and many friends whom he often visits. He has supported cultural events, and has supported the treatment of AIDS.”

Mr. Torrance estimates that his friend turns out about four novels a year. “He is extraordinarily prolific. But he is also a very fine academic,” he says. “He chaired the Bioethics Council in Britain and was a professor of medical law at the University of Edinburgh. He is wise and kindly and, obviously, funny. Another of his activities that is very amusing is that he founded The Really Terrible Orchestra, in which people who can play an instrument very well decided to play another, just for fun. He’s an amateur bassoonist. When you came in, you were given a brown paper bag to blow up and explode during the 1812 Overture.”

Mr. McCall Smith also helped found Botswana’s first center for opera training, the Number 1 Ladies’ Opera House, for which he wrote the libretto of their first production, a version of Macbeth set among a troupe of baboons in the Okavango Delta, according to Wikipedia. He lives in Edinburgh, where he was professor of medical law at the University of Edinburgh and is now emeritus professor at its school of law. He was appointed a CBE (Order of the British Empire) in 2006.

Mr. Torrance said he and Mr. McCall Smith had talked, over the years, about making Mr. Torrance a character in one or more of the author’s books. He does appear, more than once. “I have a passing mention in 44 Scotland Street,” he said. “But I am also in the Isabel Dalhousie novels. In the most recent one, I preside at her marriage. So I almost feel that I know her.”

About a decade ago, Mr. Torrance delivered an academic paper at a former monastery in the Netherlands. “I came to the seminar room one day, and sat down, and a professor of history from the University of Basel sat beside me and put down a heap of books on the table,” he recalls. “On the top of the heap was one of Sandy’s [Mr. McCall Smith’s] novels about Botswana. I asked him about it, and he said, ‘I get my students to read these books because it helps them to get a feel for contemporary Africa.’ I thought that was quite a tribute.”

Tickets to “An Evening With Alexander McCall Smith” are $25-$35 ($15 for students); $50 and $75 for those wishing to support the Friends of the Princeton Public Library. The $75 ticket-holders will sit in the best seats (rows A-H), receive a copy of the author’s latest book and attend a pre-show reception. Those at the $50 level sit in the specially reserved section and receive a copy of the book.

“The great thing about Sandy, apart from his being highly informed, intelligent, and observant, is that he is very kindly,” Mr. Torrance says, summing up his friend. “He’s real.”