I don't recommend doing what Naomi and I did, which is read through the Mercy Thompson books back to back. It becomes reasonably clear that the reader is getting roughly the same story with different covers. I've spent a lot of time considering this; the series has many ardent fans, and I used to be among them. I think it all depends on what one enjoys in a story, and how tolerant one is of repetition. I'd rate my tolerance somewhere in the middle, but only until the tipping point occurs, either through saturation or through pet peeve. I think series like this are best enjoyed exactly as they occurred: published one at a time, a year in between. Then the repeated explanations and summaries don't irritate, they only recall, taking on the cadence of storytelling, when the reader slips into the story world with the beginning "long, long ago and far, far away..."
Despite a reliance on folklore and fairy tales, the Mercy Thompson series is and remains a sanitized, muted version of those grim worlds. The slavering wolf can actually control themselves, if they are old and really powerful. The strange fae will probably help you if you amuse or respect them, but even the bad ones won't trap you for years until everyone you loved has died. Scary vampires exist, but a sheep necklace can protect you; there's also a vampire that wears t-shirts and watches movies. None of the wolves go crazy despite frequent assertions that it can happen. No one except bad guys are ripped apart. Even vampires can repent. Victims are saved. Misguided humans are coached. Almost everyone gets a chance to redeem themselves. There's very little true evil. No one even swears. I note it because while it is one of the things I enjoy, that sense of ultimate goodness and happy endings, I also believe it explains part of the series' popularity.
Unfortunately, familiarity also enables recognition of faults, and there are quite a few. The overall series arc lacks a sense of coherency. After reading through a number of the Briggs' family posts, its clear that the series expanded to accommodate popularity and not out of an internal sense of story progression. The first was written; Blood Bound came about because the first did well, followed by a surprise contract to buy three more books. I'd contrast this with another favorite author, Ilona Andrews, who had a clear arc for a seven-book series and a sense of where it was headed in both story and emotion. The plotting to date in Mercy has been roughly the same for each book: someone is imprisoned and with Mercy's special powers, the group will save the day. This is true in Moon Called (Adam), Blood Bound (Stefen, etc.), Iron Kissed (Zee), Bone Crossed (Mercy) and Silver Bourne (spoiler/Mercy). The emotional plotting is also startlingly similar: Mercy will have trouble trusting her affection for Adam. After mistrusting him when she should not have, he will still support her and she will vow to trust him. At the same time, one of the powerful people she loves is willing to sacrifice/suicide.
Binge-reading also draws attention to a narrative containing a lot of telling without showing. Mercy will have asides in every book telling about her history, the fae reservation, werewolves, the wolves' coming out and her relationships with Samuel and Adam. Usually she will also educated the reader on Zee and the Grey Lords, and Stefen and the seethe. I think this is generally forgivable to many readers as the familiarity echoes the storytelling tradition, and the ritual of description, but again distance makes the heart grow fonder.
But those are mostly academic issues. What I've found less personally enjoyable, and perhaps even less forgivable are the roles women have in the series. Which is very little: Mercy operates in a man's world, both figuratively and literally. Mercy herself demonstrates no particular direct agency; all of the plots start with her reacting to an event that happens to her genuine, unsuspecting little self. The reader is quickly introduced to the idea that women associated with werewolf packs 'hate' Mercy, and that becomes an ongoing theme through the series. Even human women dislike Mercy, as Gabriel's mom Sylvia does. The exception to agency is Blood Bound, where the evil and conniving Marsilia engineers an elaborate trap, although clearly she still hates Mercy. I realized that even side characters are almost universally male with the exception of a couple of inscrutable fae. The only exceptions being Mercy's mom--who is never more than a whirlwind in and out of the scene--and Adam's daughter, Jesse. I found it disappointing, particularly from a female author with girls of her own.
Silver Bourne was the gestalt for me, highlighting all the redundancies. It comes as no surprise then, that a book lent to Mercy by a bookstore owner (male) may have other properties, and that the werewolves in the pack are still trying to break Adam and Mercy up. Samuel is sick at heart and only his wolf saves him, and now Mercy must save his wolf. Mercy's home is targeted. Someone is kidnapped and Mercy must save them, and Adam endures several challenges. Samuel's depression plot was solved very easily and tritely by L-U-V, which I thought disappointing after the complicated emotional fallout of the rape back in Iron Kissed. It was the last book of the series I bought, back in the day when I was silly enough to still auto-buy authors.
Three and a half redundancies, rounding down because that's what I did last time.