Book the Second in the wonderful Veronica Speedwell mystery series by Deanna Raybourn! 
 Victorian era? Check. 
 Intelligent, non-conformist heroine? Check. 
 Flouting of social niceties? Check. 
 Sexy, mysterious partner, and oodles of sexual tension? Check, and check. 
 Oh, and not incidentally: A ripping good murder mystery? Yup, big check. 
 Prolific author Deanna Raybourn released the first Veronica mystery, A Curious Beginning, in 2015. (I reviewed it, here.) In it, we met the irrepressible Veronica Speedwell, an accomplished lepidopterist in her mid-twenties who finds herself suddenly at the center of strange plots and attempted violence. Veronica is headstrong and unabashed, and while she has the gentility and manners of a lady, she is quite proud of her scientific accomplishments -- and is quite blunt about taking lovers during her overseas expeditions and her general enjoyment of the carnal arts. 
 I blinked again. "Is it not possible to enjoy bed sport during one's pregnancy? You mean women have to go without for the duration? Nine months without sexual congress? That's monstrous." 
 By some odd twists and turns, she finds herself under the protection of Stoker, a (gorgeously muscled) man of good family who is haunted by clouds of scandal and mystery stemming from his own natural history expedition which ended in disaster in Brazil. 
 Side note -- a word on Stoker's appeal: 
 When a gentleman of excellent breeding and perfect vowels assumes the guise of a ruffian, women are frequently reduced to a state of helpless infatuation. 
 The two end up on the run together, trying to figure out who's out to murder Veronica and why. It's absolutely fun, full of hijinks and smart, quippy dialogue. Veronica and Stoker quickly became one of my favorite non-couple couples in fiction! 
 In A Perilous Undertaking, Veronica and Stoker are somewhat in the doldrums after a planned expedition is cancelled, until Veronica is summoned by a mysterious upper-class lady to take on the task of absolving a condemned man of murder. Lacking much else to do and needing a challenge, as well as fueled by a personal motivation that I'll leave unspecified (spoilers!), Veronica accepts her assignment. With Stoker as her sidekick/co-adventurer/protector, she sets out to explore the world of a bohemian artists colony, its patrons and participants, and the secret and slightly kinky goings-on that a whole slew of people might want to kill to cover up. 
 She fell silent, gripped by genuine emotion, and against my will, I found myself in danger of liking her. For a potential murderess, she was rather engaging. 
 Once again, Deanna Raybourn creates a highly entertaining adventure that lets her characters shine. Veronica and Stoker are quite a pair, and you could cut the tension between them with a knife. They live and operate outside the bounds of proper Victorian society, yet they're able to infiltrate into the upper reaches and still maintain their zest for scientific knowledge and experimentation. 
 Some rather comical incidents (including encounters with a large and inconvenient tortoise) lighten up the tension of the more dangerous escapades. There are injuries, life and death situations, narrow escapes, and acts of great daring. At the same time, we learn more about Veronica and Stoker's inner lives and what makes them tick. 
 I think it's pretty obvious that I loved the heck out of this book! The characters are just so delightful. I only hope that the author continues the series, as I want more! Veronica and Stoker clearly have plenty of adventures ahead of them and, at the risk of sounding completely voyeuristic, I want to get to see where their relationship goes, when and if they finally take the plunge and acknowledge their mutual attraction. 
 I suppose you could read A Perilous Undertaking on its own, as there are enough hints and reminders sprinkled throughout to cover the essential backstory -- but why would you want to? Start with A Curious Beginning, then continue straight on to A Perilous Undertaking. You're in for a treat! 
 Note: Review copy won in a Goodreads giveaway, with thanks to Goodreads and Berkley Press. This review also appears on my blog, Bookshelf Fantasies.