Don’t produce a magnum opus on LTUAE
Writing a book is a great thing to do and should bring you a great sense of achievement – and rightly so. Some writers get carried away, however, and try to cram too much into their work, therefore clouding its focus.
It’s the trap of producing a Magnum Opus on Life The Universe and Everything (a la Hitchhikers Guide To The Galaxy). In other words, throwing material that isn’t relevant to the topic at hand.
Don’t be tempted to lose focus on go off on tangents that you think are interesting. If it’s not on topic, save it for the next book!