With the 6th book's release date approaching, I thought I'd share some of my theories for The Desolations Of Devil's Acre (spoiler alert for TCoTB)
Don't hesitate to add your own theories!
Leo was willing to stop chasing Noor and agree with the ymbrynes so easily because Caul proposed him something better (since Caul can literally "talk" with anyone, he could have talked with him too)
Some of the wights might turn against Caul (I'm thinking about the ones captured in Hopewell, who Jacob described for the first time as looking uncharacteristically defeated)
Similarly, some ymbrynes might turn against the other ymbrynes and join Caul's forces, especially the ymbrynes in training and especially Francesca. She seems to know too much, and I think the Bentham brothers proved again and again that knowing too much ends up badly
V is actually alive (yes, wishful thinking, I know). I mean, she's a fierce hollow-hunter and an ymbryne. She must have some tricks up her sleeve
Speaking of V, she is called the "mother of storms." We literally saw that, but what if this was meant figuratively as well? She might be Noor's adoptive mother, but she's still her mother. Storms typically have lightening, and Noor controls light (which might look like lightening if she produces a huge amount of light like she did at the end of AMoD). What if the "storm" was also Noor? Perhaps it's a hint at the massive powers Noor will have to use along with the other emancipators to defeat Caul
We have already met all seven emancipators. Jacob is probably one of them, along with Miss P
Caul is not the only one who's back. Myron might be back, but the line "the old ones from their sleep are torn" makes me think that other ancient souls from the Library will be resuscitated too. And given how some of those souls were described in LoS, it's not going to be pretty
I've said it before, but I'm not fond of Sharon's little meetings. Sounds a lot like the beginnings of the Claywings. I don't really trust Sharon anymore. Bonus points for Jacob hearing sounds of "rats" when he dreamt of Caul in AMoD, and for both the recipe and the beetles being stolen from Myron's house by the wights (it's stated that Sharon knows the place better than Bentham himself, so perhaps he's the one who gave up the location of the recipe and the beetles)
This is getting way too long, I'll probably write the rest on another post.