Curious to hear your thoughts on this. Do you find maps, family trees, or other 'bonus' material helpful, or do you just flip over it without checking it out?
I'm working on #2 & #3 in a time-travel historical romance, the sequels being longer and more complex than the first. There are quite a bundle of characters, so many so that I have my own stockpile reference to organize them. Many of the characters are entwined and their origins are diverse.
I also have some maps of the time period, which I changed for my own fictional purposes.
As a reader of a series, would you be interested in a family tree with key details to refer to? Or a map of the area the characters lived in?
I will say that I do not think my story is terribly complicated. I don't think the reader NEEDS this information, but in some cases I think they may enjoy it.