How many episodes are in a season, and how long is each season?

This varies from book to book. Some seasons may consist of as few as one episode, some as many as eight or more; it all depends on where the natural conclusion to the season arc falls. On average, however, an episode in a serial story will be 15,000 to 20,000 words (roughly 55 to 75 pages), and an average season will consist of three to five episodes.