Using side stories to help promote a main novel.
This isn’t the same as when readers of a novel urges you to write a sequel. A side story might be in the same time line and characters and settings might be referenced but it shouldn’t depend on the main story to work.
I have a science fiction series, Flying Crooked. A fleet of ark ships leave Earth and SUPPOSE WE is one which crashlands on a goldilocks planet. Sadly, the natives are so far in advance of Earth they ignore the humans appeals for help. FALLING UP was its sequel and others are in the pipeline. STEP FORTH is another ark ship so is known to SUPPOSE WE, but its AI has been corrupted. Now the ship thinks it’s human and so busily tries to eradicate what it believes are vermin on board.
I found a good publisher of webzines, Aphelion which offers free reads to the public. They accepted I THINK, THEREFORE I AM and hopefully, readers will go on to find the full novel and series.
Note: the name of the confused spaceship, STEP FORTH was suggested by author Mark Iles to go in conjunction with SUPPOSE WE the other ark ship. Hence, suppose we step forth. I liked that.