You may want to start out with novellas, they are books that are longer then a short story but shorter then a novel. Another thing you could do is try sketching out characters, adding more to them as you discover more about them. There are stories that go extremely into detail as well, I don't like those kinds of books because for me they drag but they might be more your cup or tea.

Also you don't have to read just one book at a time. Some people do because they find reading multiple books overwhelming but for me once I get kinda bored with one book I move onto another to read for a while then come back.