Also, the mystery in The Sinister Pig was not particularly suspenseful and was therefore fairly unsatisfying. We learn early on who's behind the murder that occurs at the end of the first chapter, and it's understood in a broad sense what his motivation was, so the only thing left to be uncovered was the specific details of the criminal enterprise that he was organizing. And everything seemed a bit too contrived, even by mystery novel standards. I think writers ought to be allowed one major coincidence per book. So having established at the end of the last book that Bernie Manuelito was leaving the Navajo Tribal Police, it was acceptable for Hillerman to give her a new job that just happened to place her in a geographically convenient locale. That's your one coincidence, and that means you can't use another one without straining credulity. Unfortunately, Hillerman uses several more, leading to a dénouement that is rather implausible.
Lastly, The Sinister Pig contains very little of the local color and insights into Navajo culture I've come to expect from Hillerman. Of course, much of this novel takes place off the reservation, so perhaps that's to be expected. But couldn't we have read more about the all-Indian Border Patrol unit to which Manuelito was assigned, or about how she felt about living and working so far from her own tribe? I think so.
Nevertheless, as a fan of this series, I still liked it. That's because, as I said before, I care more about the personal lives of the characters than anything else. So how can I not like a novel that's as much about the relationship between Jim Chee and Bernie Manuelito as about anything else? How can I not chuckle at Chee expressing mock surprise at Leaphorn pulling out a map to put all the pieces together, or at Cowboy Dashee's good-natured insults about the Navajo? As indicated above, I would have liked to see more of all the regular characters, but what there is is cherce.
Bottom line, if you're a fan of Hillerman, you'll probably like The Sinister Pig even while finding it somewhat unsatisfying on certain levels. But I wouldn't recommend it to someone who isn't already very familiar with the characters