Okay, since Robin has brought up the Jason Bourne thing, I see I have to pull out this gem of a Harlequin romance, found at the library’s used-books table:
Unauthorized Passion, by Amanda Stevens
From the back cover:
Jack Fury had been watching Celeste Fortune, waiting for the right moment, the right mood…to coincidentally meet her to save her from a killer. But there was something he didn’t know about the sexy Celeste…she was an imposter!
Cassie Boudreaux had been impersonating her glamorous cousin Celeste while she was on the lam. For Cassie, who lived a safe, nondescript life in a small town, it was the chance of a lifetime — adventure and excitement as Celeste. But she didn’t bargain on a sexy protector like Jack or a killer in pursuit. Fortunately, with her new identity came new freedom — and she’d need Celeste’s entire feminine arsenal to outsmart one man and seduce another…
Jack Fury? Celeste Fortune?? Feminine arsenal??? Oh, my. (And yes, it turns out there’s an eHarlequin.com, where you can purchase a copy of your very own.)