I've now had two occasions where in writing the third book in a trilogy, I've needed to go back and rewrite the second book. (Thankfully, the first books usually seem to stand alone, for some reason.)
It's fine. It's a good reason to write the whole trilogy before I do anything with them. The hardest part is when the trilogy represents one storyline. I prefer to have each book stand alone, but there is usually a larger plotline going on that has to be tied together. Which is pretty complicated. Each book usually has it's own theme and characters, and they all have to be brought together in a way that makes sense and is satisfying.
This is different from the Series where I have may have a unifying character and world, but there isn't one over-arching storyline. I can write the Virginia Reed Adventures in such a way that a reader can read them out of order and not lose anything. The same is true of the Lander series. Each book stands alone.
The Vampire Evolution Trilogy and the Tuskers Trilogy are each one big story, which turns out to be a pretty challenging thing to do. Though there is something satisfying about it. (Not least that when I'm done, I'm done.)
Anyway, I'm stuck at 2/3rds of the way through Tuskers III. Partly because I know I'm going to have to rewrite Tuskers II, and I feel like I should do that first before tackling the end of III.
I'm waiting for the editing of book II to come back before I tackle II. I've learned a lesson over the last few books -- that having multiple versions and then trying to consolidate them is a nightmare. It isn't terribly efficient and no matter how hard I try, I tend to drop a few nice sentences or plot points by accident because it is incredibly complicated.
So I've decided from now on that if I have multiple editors (including myself) that I will edit these books successively instead of concurrently. It will take longer waiting, but should make things much easier.
I also woke up this morning determined to finish the first draft of both Tuskers II and Tuskers III by the end of the year, no excuses. Just do it. I think more than anything I've been missing the resolve. So my goal over the next few days is to jump full speed into writing on December 1 and finish these books.
2 days ago