John Buchan (1st Baron of Tweedsmuir) wrote the The Thirty-Nine Steps in 1915, but the 1935 Hitchcock film, The 39 Steps (note slight name change) may be more familiar. Criterion has a fantastic blog that abstracts the movie; stills and commentary. (Criterion Collection release available here). I love it as an early thriller, and soft spot for me due to the Scottish locations. We lived for a while near Tweedsmuir, in Broughton, now home to the John Buchan Center.
Want to read it right now?? You betcha... Bartleby lets you read the full text online here; an awesome resource.