The Case of the Misplaced Hero was originally written as a twice-a-week serial for the Daring Novelist blog. Here is the whole story collected into one novella-length volume -- 42 episodes, plus the teaser episode that leads into the next story.
When Alex was a child his eccentric aunt gave him a ring and told him that one day he should go jump in a lake. He never knew what to make of that, and never tried doing it, until one day at college, he tries to rescue his drunken professor from falling in a river. They both plunge in... and come up in a very different river, in a land that reminds Alex very much of the stories his aunt used to tell: a world like old adventure books and silent movie serials. It's a dream come true, except that his drunken old professor gets himself lost and arrested. Alex must find and rescue him, and return him home, before the old fool gets shot as a spy.