Her Favorite Forever by Caroline Lee

She’s in disguise. He’s in denial. Hijinks are inevitable.

Lady Rosie Hayle has always loved Bull Lindsay…but he’s never seen past the girl she used to be. So when he needs an art expert for his latest case, Rosie dons a mustache, calls herself Robert, and proves she’s exactly the partner Bull needs—in more ways than one.
Bull Lindsay has always trusted his instincts…which is why ‘Robert Hoyle’ sets them all on edge. Smart, talented, and oddly familiar, his new expert is hiding something. When the disguise comes off and Rosie is revealed, Bull’s carefully constructed world tilts on its axis. She’s brave. She’s brilliant. And she’s absolutely, devastatingly perfect.

Now they’re hunting a blackmailer across Scotland, going undercover as an engaged couple, and pretending their chemistry is just for show. But despite her family’s enemy staying one step ahead, a ruby-necklace-mystery spanning generations, and Rosie’s terrifyingly overprotective father (with fists that have broken necks) on the prowl, the biggest danger might be to Bull’s carefully guarded heart…

Warning: Contains creative cursing courtesy of Demon Hayle, enough disguises for a theatrical troupe, an age gap that truly doesn’t matter any longer, and a hero who finally realizes the perfect partner has been right in front of him all along.

This is it: the book you’ve been waiting for! Bull versus Demon, with headstrong firecracker Rosie refereeing… An utterly delightful way to wrap up this super-spicy series—equal parts mystery, mischief, and mayhem. You’re going to have so much fun!