Cross-posted at booklikes. 
 Makenna "Mac" Fraser, a transplant from small-town North Carolina, is just beginning to adjust to life in the Big Apple. Getting used to her new job as a Seer for the SPI (Supernatural Protection and Investigations) is a trickier prospect. As the only Seer in the region, Mac's ability to penetrate the veils that hide the supernatural world from the rest of humanity are practically invaluable to SPI investigations. The short, blonde, frail Mac isn't exactly tough crimefighting material, so she's been paired with the supersoldier-ex-cop-monsterhunter Ian Byrne, and he's not precisely thrilled to act as her babysitter. Mac isn't one to let her lack of skills and experience stop her, but when she decides to do an off-the-books nachtgnome irradication for a friend, she stumbles right into a far more serious crime. A pair of killer monsters--descendants of the legendary Grendel--are loose in the city and looking for some long-delayed revenge. If SPI doesn't stop them before New Year's Eve, it won't be long before the whole world catches on to the supernatural shenanigans... 
 The Grendel Affair is a fast, fluffy read. The basic setup is essentially a bowdlerized and gun-porn-free version of Larry Correia's Monster Hunters International (MHI), and the overall plot is the standard secret organization/race-against-time storyline. The style and characters felt very similar to those in Shearin's full-fantasy Raine Benares series. Like Raine, Mac is a low-power female saddled with some seriously significant supernatural skills. Like the Raine Benares series, the plot is lighthearted, the main protagonist is engaging, the cast is full of comic relief, and the romance is kept to a very low level. If you enjoyed Raine Benares, then definitely give this book a try. However, while I loved the idea of Revenge of the Grendels, the strong similarities to MHI, gaping plotholes, and some character issues meant that The Grendel Affair isn't going to make it on my favourites list. 
 Mac is a reasonably likable protagonist, but while I appreciated how Shearin used the Seer skillset to avoid the standard superbadass-tough-girl female of urban fantasy, I had very mixed feelings about Mac herself. Mac is klutzy, delicate, and pretty, and has a disturbing tendency to get herself into damsel-in-distress situations. At the opening of the story, I was vastly irritated by her combination of stunning incompetence and impressive self-assurance. As the story continues, even she begins to recognize just how clueless and incompetent she actually is, but she trades her overweening self-assurance for angst and self-doubt. Her feminine flutterings also seemed inconsistent to me; she's supposedly a country girl who has done her share of hunting. How can it possibly be harder to shoot a ravening monster than a solemn-eyed deer? It was frustrating to have a female protagonist who really did require a babysitter: while her comparative weakness could be due only to her self-doubting unreliability as a narrator, she gives plenty of factual instances of failure, such as the time she lets someone get kidnapped right in front of her without pulling her gun or putting up any sort of fight. Throughout, Mac highlights just how incompetent she is compared to her male peers. She repeatedly makes stupid decisions, freezes up, and gets herself into situations that she can't handle and that force one of the men to rescue her. As Ian the babysitter tells her,"I'm learning that when I take my eyes off you, all hell's liable to break loose, so watching you is safer for everyone."While I'm not big on supergirl protagonists and I like how much opportunity Mac will have to grow throughout the series, I kept wishing for Mac to exhibit just a little more competence once in a while. At the same time, I liked Mac's narrative style (and massive cookie addiction); I'm a subvocalizer, so I heard the whole book in her Appalachian accent (she's from near Asheville, NC) and enjoyed every minute of it. 
 While the story makes for a fast and easy read, I think it lacked a certain substance or solidity. I don't think Shearin put a lot of thought into her worldbuilding. Even the more imaginative touches weren't precisely original--for example, her holy-water paintball gun is ripped straight out of Jim Butcher's Dresden Files. Most of my issues with the book are entirely my fault. I'm a nitpicky, OCD reader; while I can easily suspend disbelief about magic, mayhem, and monsters, flaws in the story's internal logic drive me up the wall. Shearin's story takes place within a super-secret, super-hardcore organization, so to me, the massive security holes and impressively myopic, unprofessional actions that serve to push the plot along came across as plotholes and dented my ability to enjoy the story. Take the issue of doppelgangers. Doppelgangers are apparently a common problem in Mac's world, yet the top-secret SPI has no basic measures in place to prevent infiltration. How can Mac's adventure possibly be the first time they've been up against doppelganger problems? 
 The epic logic fail doesn't end there. 
 (view spoiler)[ 
 For example, why on earth do they assume that because they know a doppelganger was involved, they have the correct "version" of Mac now? She could have easily been replaced at any point within the story, both before and after the discovery of the doppelganger. How is it that after they know a doppelganger is present, they don't make any major security changes? Even assuming that doppelgangers have precisely the same biomechanics, fingerprints, DNA, etc. as their victims, even in our world, a standard security measure is ensuring that no employee swipes in twice without swiping out. Plus, given the existence of doppelgangers, SPI employees should have decided upon a set of "secret questions" that can be asked on demand with both true answers and dummy answers, where the dummy answers immediately indicate that security has been compromised. These questions should be repeated in a non-discernable pattern and changed regularly. Additional secret questions should be saved back for verification in extraordinary times. 
 Doppelgangers were far from the only plotholes in the story. A few of my quibbles: 
 --If you're going to use monsters to prove the existence of a hidden world, why use grendels? Since they don't have any superpowers other than strength and toughness, aren't they imminently explainable as a newly-discovered species or a genetic experiment gone rogue? 
 --Why keep only one copy of the plans? Given that one of the baddies had the thumbdrive, why not make copies? And why on earth weren't the files encrypted? 
 --Why abduct Ollie? 
 --Why put his toupee in the refrigerator? What possible purpose could be served, other than alerting the SPI to danger? 
 --Even the opening with the nachtgnome was irritating. Not only did it highlight Mac's staggering incompetence and even more impressive self-confidence; it also had an irritating logic fail: they had three bottles of alcohol. Three. Why did they give up at two? 
 --While I liked the paintballing (despite its Dresden Files derivation), the use case is illogical. Why not spray the entire place with a wide-angle paint sprayer? Paint, water, or anything else would have made the monsters visible. There was no need for a seer or a precision shot except to make the plot more "exciting." 
 --Another plothole was introduced by the camera scene. Since Mac can see past the veil via camera, why did she travel with one group down into the underground? Why not keep the incompetent, untrained Seer nice and safe by leaving her at SPI Headquarters and using a camera? That would also give her the opportunity to supervise all of the groups at once. Seer skills working over camera shots just opens up way too many possibilities that Shearin didn't consider. 
 --And then there's the tequila gun. Call me a pyro, but that's a perfect opportunity to set everything on fire. 
 --Even the origin story is a little fuzzy. Why did they manage to pick up on the veracity of Mac's skills from a National-Enquirer-style story? 
 (hide spoiler)] 
 As with most of my plot nitpicks, these issues could have been easily explained by some creative thinking or even a little judicious lampshade hanging. Yet again, I really, really wish there were such a thing as Plothole Beta Readers. They would save all the OCD readers like me a lot of tooth-grinding. 
 All the same, there are plenty of aspects of the story to enjoy. Beowulfian monsters are always a win, and I liked most of the characters, including the Russian werewolf and the (literal) dragon lady boss. I even rather liked the ever-put-upon and ever-patronising Ian. SPI also seemed like a fun place to work--I loved the little details like the coworker-donated desk trinkets. Overall, The Grendel Affair is good clean fun, and I can definitely think of worse ways to spend a few hours. 
 ~3.5 
 ~~I received this book via the Goodreads First Reads program.~~