1) The author killed most characters I cared about on the first book.
Game of Thrones was a series where I endured the death of a lot of my favorite characters, and its last tv season was *spoiler alert* so tragical! All hopes for my favorite characters, Daenerys Targaryen and Jon Snow, were crushed in the worst possible way. Even though I read all the released books in the series so far and will probably read the next ones (when its ‘wizard’ author finally publishes them).
This was tough, an exception, because there were many awesome characters still left and even if my reader’s heart got broken five times or more in each book, I still had other five awesome characters to follow on the next one. (Furthermore, Tyrion Lannister was staying to the end, saying he was “the god of t**** and wine”).
GOT exception apart, I won’t be doing that again, especially not for five books in a row. If an author kills my most loved characters already in the first book, don’t expect me to hang around (no, no, no, enough with the heartache).
I have a really hard time understanding why authors make us, not only like, but tie all our heartstrings, to a character, show all her/his potential for all those series sequels to come, and not long after, after one hundred pages, kill them. Frankly, I’m not supporting this further.
Imagine how it would be if Dorothy had never journeyed through the yellow brick road, met the Wizard of Oz and melted the bad witch? As a reader, I’m Toto following Dorothy, and I’m not going anywhere without her.
2) The author changed the main characters from one book to the next.
I like when a story world stretches longer than three books. But for me, the longer and deeper character journeys that happen during more than one book, in a well-written series, is the most important reason why reading a series is enjoyable for me.
I consider very jarring if the main characters are switched for completely new characters already on the second book, or any next book in the series for that matter. Then, instead of following the amazing plot with the characters I already care about, I have to get acquainted to new points-of-view once again.
It also creates a multitude of superficial characters to populate a series, and that, for me, is usually less interesting than characters who have a personal journey at each new book. I would rather follow two characters for three or many more books.
My upper limit so far has been ten books and I could see myself following a character even longer, if its journey would be interesting enough to go on following, then follow six main characters that had their whole story told in only one book.
I understand that going that deep into analysing a main character is much harder for the author than creating yet another fascinating and superficial first impression, but I like character layers, depths, baggage and flaws. The first book is like the small talk of a conversation for me, the sequels is where stuff gets real and finally interesting. The sequels are when all those skeletons get out of the closet and the flashing characters turn from wooden puppets into real boys/girls/non-binary characters. 😉
And when it comes to plot, it’s better when a second book is done with the main character introductions. Now it’s time for development, deepening what I know about that characters I already know a bit about, so let’s move on with the story. If the main characters I liked in book one become secondary characters, it’s way too jarring. Their story and POV was the main reason why I was invested in the series sequel to begin with, and I rarely like spin-offs. Specially spin-offs posing as sequels. As a reader I feel as if I was promised a second book, so a first book with the same story world isn’t the same. I get that feeling of “this wasn’t the dish I ordered”. It may taste wonderfully, but it’s like ordering salad and getting pizza, or the other way around.
I have suspended my disbelief while following Dorothy, I don’t want her to find out about the Ruby Slippers and come back to Kansas before the story is told. I don’t want either to follow Dorothy’s daughter that picked up another tornado elsewhere and had other witches to melt. That story is already told. Dorothy’s daughter might become an alien hunter and have a completely new story in an a Moon in Saturn, but don’t kill her before her series is done either.