It pains me to give this a one star rating because it's obviously not a nice thing to do, but at some point honesty has to win out, right? 
 Let me start out by saying that I did enjoy Truthwitch, enough to give it a FOUR STAR RATING, although I also thought there were a lot of issues with it. It felt like an amalgam of elements from basically every fantasy series that I read while growing up, which I know for a fact were influential for Sarah J. Maas - authors like Anne Bishop, and Jacqueline Carey. Now, since S.J. Maas was (formerly, it seems) BFFs with Susan Dennard, it wasn't too surprising to see the same kinds of themes, characters, and even worldbuilding. Like, it doesn't take a lot of critical thought to think that hmm, Aeduan with his oh-so-special daggers is just teensy bit like Joscelin from the Kushiel Trilogy, and I've left a few long reviews already on Maas' Throne of Glass books about all the Anne Bishop and Jacqueline Carey, ah, inspirations. In any case, taking inspiration from authors that I admire isn't necessarily a bad thing because there's a reason why I like those authors in the first place. I think this is really why I struggled with Truthwitch at first but ended up liking it so much in the end. 
 I should also probably mention that I only picked up Truthwitch because I knew that Dennard (is? was? seems like they had a falling out) friends with S.J. Maas, and I've been following Maas for over a decade at this point, all the way back in the early days when Throne of Glass was a story posted on FictionPress (heck, probably when it was still newly split from Fanfiction.net) as "Queen of Glass." Make of that what you will. For me, I tried hard to like Truthwitch and it took me ages to get into it - I must have read the first part of the book three times at least - but when I finally did, I was sold on the concept. Were there lots of things I thought needed improvement? Sure. But Iseult and Aeduan - well, particularly Iseult - won me over enough that I didn't mind skimming the Safi/Merik parts. 
 All that said, I'm definitely not going to be reading whatever books come after this one, because I could BARELY force myself to get through this one, and that's after powering through in about two and a half hours. 
 What problems did I run into? Well, where to start? One of the main issues with Truthwitch was that it took ages for the reader to figure out what the story was supposed to be about. I mean, I got from the blurb that Safiya and Iseult are some prophesied duo destined to fix the magic wells and save the land, blah blah blah... I also got from the blurb that Safiya is a truthseeker (minor gripe here: does everything really need to be turned into a title with a capital when it's obvious what the word means?) and Iseult can basically read the "threads" of a person's life/fate. Other than that? I had a very, very hard time caring about the lands they were from, whatever treaty they were trying to put together, or where the plot was going. 
 Remember how I mentioned I had to read the beginning of Truthwitch at least three times because I just couldn't get into it? So basically my most vivid memory of that book is the failed random highway robbery scheme that opens the book, which I never DID really understand why they did it other than something about Safiya just being naturally impulsive or something. 
 So, Windwitch opens in a similar way and the reader is dumped into Merik's POV. Apparently some time has passed, but let me tell you, there is zero reintroduction of the past events/storyline for the reader. I'm not normally a bad reader and I do have a very good memory for stories, but since Truthwitch never made that much of an impression on me, I was definitely kind of lost. Like the first book, the author just jumps straight in with a lot of jargon (Capitalized Jargon! Everyone is a Something and has Fancy Though Utterly Unimagintive Titles!). 
 Ok, let me just take a minute here to whine about the overall state of YA fantasy. I think I've just about reached my limit on authors being too lazy/unimaginative to name crap and thus deciding to just capitalize common words or adjectives. 
 I mean, seriously. This series alone has such shining gems as Old Town. The Fury. Judgment Square. The High Council (or, even better, the Council). The Battle Room. The Royal Forces. The Puppeteer. The Cleaved. The Purists. The Adders. (Not to be confused with...the Adder High. Ok, I guess she tried with that one?). Even the insult of heretic, for some reason, is transformed into Heretic. Why? I have no clue! And wow, the Contested Lands, those definitely are so very, ah, contested.ALL FROM JUST THE FIRST 100 PAGES.. 
 But seriously, every other YA series seems to think it's absolutely brilliant to just stick a capital on a word and make it a place. Yes, places like that exist in the real world and done right, can add balance out fantasy names to add realism to your world. No, that doesn't mean your entire book should have such scintillating descriptions like The Dress, The Key, The Jewel, The City, The Duchess, The Freaking Guard. Why not just throw in The Bad Guys while you're at it. 
 Anyway, what happens during the other 250 pages of Windwitch? I sorta know, but the main reason why I "sorta" know is that I just don't care. There's a lot of action but not a lot of clarification on where it's all going. We have kingdoms and empresses and evil magicians, but the plot is somewhere lost between all the endless, overly detailed fighting scenes. I mean, literally, one such scene opens with this amazing line: "Safi versus Kahina." It's followed up with two full pages of kicks and blows and ducking. It's almost like someone forgot to delete an editor's bookmark to cut down on these dragged out fights. 
 YMMV and all that, maybe these just aren't the books or series for me. I'm probably more snarky in this writeup than the book really warrants, but chalk it up to my frustration over feeling like I wasted my time trying too hard to read this and trying even harder to like it. 
 One last thing: characters dropping into random songs or little poetry verses/rhymes? I've been reading for a long time and the only authors I can think of who can pull it off are either a) epic fantasy authors like Tolkien or b) people like Brian Jacques, who made it fit well in his Redwall series. I'll be the first to admit that, when I first started writing, I was guilty of the same temptation to dump little cutesy (I liked to think of them as poetic) verses here and there in my writing too. Heck, I once opened my 300k word LOTR fanfic with some of two of the most dramatic, cringe-inducing verses ever. I mean, all these awesome authors are doing it, why not me? The answer: It's damn hard to do it right. Someone should've advised Dennard to ditch the attempt and find a better way to convey what she wanted.