What to Expect
Peace Talks picks up where the series previously finished (some 6 years ago), and continues on the main story arc. Harry had been fighting the Fomor, which came to power after his war on the Red Vampire Court. Getting into this book is like meeting an old friend again, catching up and reminding yourself of past events. It then continues in a true Dresden fashion, with complications and counter-demands piling up quickly to a nearly impossible situation.
What I liked
I love the series, the complex and rich world that Butcher has built. As usual, there's a bit of new lore to explore, with new threats and more for us to discover about his world. Butcher's plot are thriller-style: fast-paced, with mounting complications and quickly rising odds.
Dresden himself is not without flaws, and is generally a very relatable person (you may not always like him, but at least you could understand where he's coming from). Side characters at this stage of the series are good and complex too, not cardboard cutouts. All have motivations of their own, and in some cases (Marcone and Lara Raith in particular) tend to be very interesting in their own right. In this volume we get a deeper view into Ebenezar McCoy, Harry's grandfather and senior wizard.
What to be aware of
This book is essentially the first half of a much larger work. Butcher usually wraps whatever he started by the end of each volume, leaving just a few hints about things to come when he'll explore the consequences. Peace Talks ends very much on a cliffhanger, and it's obvious that it had to be split into two volumes. The scope of the work might partially explain the time it took to finish and publish. The next installment, Battle Ground, is due out by end of September this year, so make your own choice about reading now or binging when both are out.
As mentioned above, the series has to be read in order. There are heavy references to past events, both from the main arc and from the short story collections. In terms of personality, Dresden has a distinct voice. Just like with regular people, he is who he is (and don't mistake Butcher for Dresden), and you may or may not like him. By this point in the series, you'll know.
Felix enjoys the series too, enjoys looking at the working of a supernatural world from the point of view of someone who's a top player (he himself is much more focused on occult cases that affect regular people - even when he keeps gets dragged into highly political ones). He has the sense that should Dresden ever have the time for a relaxed drink, they could share many pleasant hours shooting the breeze together over a cup of wine even though Dresden hasn't done any 'proper' occult detective work in a while. He's eagerly looking forward to the next volume, to see how the battle with what, for him, is a mythical god will turn out.
If you're a fan, why are you reading this review rather than the book itself? If you haven't read them yet, you can see my review for the full series, but do make sure you read them in order. Remember that the first three volumes are slower, earlier works, but from then on Butcher's writing is steadily improving and the series really takes off in scale and exploring consequences.