General Terms:
* Novel: This is the most common term and generally refers to a long, fictional narrative.
* Epic: Often used for long, sweeping narratives, often with a grand scope and themes. Think *The Lord of the Rings* or *The Odyssey*.
* Tome: Implies a large, weighty book, often with a scholarly or academic feel.
* Magnum Opus: Literally means "great work" and is usually used for a writer's most important or ambitious work.
More Specific Terms:
* Doorstop: This is a humorous, informal term for a very long, heavy book.
* Brick: Similar to "doorstop", but with an even greater emphasis on the physical size.
* Blockbuster: Used for commercially successful novels, often implying a certain level of length.
* Series: This applies to a group of books with a shared plot, characters, and setting. Each book in a series might be long on its own.
Ultimately, the best term depends on the specific book and the context in which you are using it.
For example:
* "I'm reading a fascinating novel about the French Revolution."
* "The author's magnum opus is a sprawling epic set in a fantastical world."
* "I'm trying to make my way through this doorstop of a book, but I'm finding it hard to stay focused."