What is the difference between the "book" and the "novel"?
Well, in general the terms are interchangeable... a book is a volume of fictional or non-fictional work whose pages are printed and bound...however, this is not the case anymore, as there are paperbacks that can be characterised as books, and books that are novels.
A novel is a book-length work of fiction, or if you prefer, the term ''novel'' is mostly use to indicate a work of fiction. It tells a story and has characters, plot, begginging, middle and end.
In the case of the Malazan books, the main ten books ''tell the story'', a fictional history if you like, events occured. Yes they can be described as novels too but they are the main plot of the whole story, whereas the so far eight novels, describe fictional events that happened in the books, or described events and reasons for leading to the events in the books, in more detail. Or tell the story of certain characters from the books. Does that make sense?