I was asked to read and review a novelette. A what? It sounds like a shorter version of a story, but just what are we talking about here? It turned out that I fulfilled the request in a couple hours.
Short stories (less than 7500 words) must focus on one character and a single event or it becomes too intricate for the length.
Novelettes (generally 7500-17000 words) still have a narrow focus. Like short stories, these are often written in first or third person narrative style.
Novellas (about 17000-40000 words) can include more characters, sub-plots, and twists.
Novels (generally 50000-90000 words, sometimes more) are full-length books that obviously include more complicated plots and elements.
Chapter books and Middle Grade (typically under 55,000 words) books have their own set of word counts and content.
Have you noticed the come-back of shorter stories? There are many reader and author benefits, including: a better time and money fit for busy reading/writing/editing schedules, a quick chance to "try out" a new author or keep fans interested between longer projects, a great place to gain exposure and grow readership, and a greater return over novel lengths for e-book rental programs that pay authors per book.
Collections (typically the same author or type of story) and Anthologies (feature various authors on a theme) are often grouped to form a novel-length book. These may be a single volume or continue on with more. Sometimes authors can get in on these by submitting to a contest or publisher; others are by invitation only. This is where networking may be valuable, or start your own group project. Seek the right market and follow submission guidelines. Authors of differing publishing companies that wish to collaborate can often work out an agreement via their publisher's project representative. Get permission and questions answered before you get too involved. Self-publishers, this is a great way to start out, write something outside your genre, or mix with other authors. In either case, understand your rights.
Lots of choices for readers and writers. Enjoy the book world.