It's not a rare word, but it's not common, either. A more common word would be "unique." The meaning of "singular" really is closely related to the word "single." It means having the quality of "single"-ness. Here it is a synonym for "unique." James says "exceptional," "distinctive," which is correct, but the literal idea is even more intense. It means so exceptional and distinctive that the person, thing, or event is the only one of its kind, there are not others. "There's never been another ship like the 'Titanic'"--the 'Titanic' was singular. Be careful: in the erotic novel "Fifty Shades of Grey," Christian Grey says "My tastes are very singular." He means his sexual preferences. Because "singular" is a slightly unusual word and because the popularity of the novel has made this a catchphrase, it wouldn't surprise me if the word were starting to acquire a sexual connotation. To be safe, say "unique."

"Exceptional", "distinctive".