I'm pretty sure I came to the same conclusion about missing info when I read this - I think the spin-off books Eternal Kiss of Darkness and First Drop of Crimson were released between these books and stuff happened in that - which annoyed me because spin-offs should be spin-offs, and it should build off, not influence the original series.
I totally agree. Novellas and spin-off books aren't going to be readily apparent to readers that they have to be read to understand the main series. I thought the spin-off books came out after the series. Guess I have to figure this out. That's another thing, readers shouldn't have to complete, like, word problems to figure out how to read your series!