There is a sci-fi series my husband loves He started with book 2 and though the books are tomes that would make great doorstops he eagerly reads them and rereads them, When he finally tracked down a copy of book 1. He hated it–said it was slow and boring and he would not have bought book 2 if he had read it first. and as he adds missed out on a wonderful series and great characters and plots. Maybe write the others and go back and redo book 1. maybe write them as non series (maybe that will eliminate your reluctance to write them then having them written you can see if they want to be a series and go about the series in the revision. clear as mud ? Your a great writer and I’m sure the next ones will knock it out of the park.