Essentially they're focussed on the experiences of Rhett, who joined the Rangers after running from the care of his 'parents' and also discovered he has the ability to shapeshift into a giant bird, just one of his powers when it comes to fighting the monsters which surround him. In Conspiracy of Ravens, Rhett was up against a sorcerer called Trevisan who subsequently possessed the body of a young girl and went on the run - Malice of Crows follows on immediately from that book and details what happens next.
Rhett's own past has always been more than a little mysterious, so more information comes to light in this volume, not to mention that there's also some degree of resolution around relationships for him. This book didn't feel quite as smoothly plotted as the previous two and just seemed to stop, with only minimal resolution, which was one of the reasons I gave Malice of Crows 4 stars when I gave the previous books 5. The other was the way in which the book ends, which felt unnecessarily cruel for Rhett given everything he's previously been through.