This is the 6513th most frequent Swedish word.
martin
"Martin" is a Swedish male given name.
Martin is a proper noun, referring to a person's name in this sentence.
Martin är en skicklig musiker.
Martin is a skillful musician.
Martin is used as a title here, referring to a character in the book's story.
Jag hittade en bok med titeln 'Martin och mysteriet'.
I found a book titled 'Martin and the Mystery'.
Martin is the name of a location, specifically a town, in this context.