The most head-scratchingly complex relationship in the Rachel Morgan series has always been between Rachel and Trent. 
 And after several books of dancing around the topic, Kim Harrison dives headfirst into the respectful-yet-antagonistic relationship in "Pale Demon." Her ninth Rachel Morgan book is a taut, lean thriller with crackling dialogue and some very unusual magic -- and the centerpiece is the baggage-laden exchanges between witch and elf. 
 While Rachel is preparing for her coven pardon and her brother's wedding, Trent reveals that he wants to take her there himself. Je also has important business in the same area -- and despite her reservations, Rachel reluctantly agrees. But their road trip is interrupted when a trio of elf assassins attack them in St. Louis. 
 It turns out that Trent is after something he's desperate to claim from his ex-fiancee, and he needs Rachel as his "mirror, sword and shield." And their road trip only gets worse as they deal with pixie tribes, hostile witches, and a daywalking demon named Ku'Sox. As the witch world turns against Rachel again, she finds that she is the only one who can stop Ku'Sox. 
 "Pale Demon" is basically about a vacation from hell that blooms into a massive supernatural battle. But under the skin, the book is actually about the relationship between Trent and Rachel, which always seems to be hitting potholes -- when they aren't practically ripping each other's heads off, they're sizzling with sexual tension. 
 And after the complicated tangles of the last few books, "Pale Demon" is a relatively straightforward book -- there's a lean, fast-paced story entangled with just a few running subplots. Harrison's prose is sharp and steely, with plenty of flashy magic battles, gory attacks by Ku'Sox, and some little moments of comic relief (Trent's "smiley face" mark). 
 As usual, Rachel is put through the physical and emotional grinder -- when she isn't grappling with demons, she's desperately trying to defend herself against the coven. Her verbal fencing with Trent makes for fascinating reading, especially since it's obvious that she's beginning to not only trust but love him. Yes, the romantic hints are piling up. 
 And Harrison takes the time to further flesh out characters like Ivy (whose friendship with Rachel reaches a bittersweet landmark), Al, and the ever-adorable Jenks ("Take me with you Trent. I've never been on an elf quest before! Ple-e-e-e-ase?") who is starting to move on after his wife's death. 
 Kim Harrison throws some shocking curveballs into "Pale Demon's" twisty plot, but the real centerpiece is the relationship between Trent and Rachel. A must-read.