First, the plot: Harry, Ron Weasley and Hermione Granger seek the remainder of the seven Horcruxes -- the physically manifested pieces of Voldermort's soul, separated and hidden by Voldemort, so as to keep them safe -- so that they might destroy them, and, along with them, Voldemort.
Meanwhile, Voldemort has quietly taken over everything. Pius Thicknesse, one of his minions, runs the Ministry of Magic; the media is monitored and manipulated by Voldemort's forces; Severus Snape, Albus Dumbledore's murderer, is Head Wizard of Hogwarts; Muggles (aka, Mudbloods) are being killed by Voldemort's wizards, via what Muggles call "accidents".
Now for the review.
It's a wonderful read. The middle section lags, when Harry, Ron & Hermione, lost, squabbling and seemingly directionless, seek the Horcruxes, even as Voldemort's Death Eaters hound them.
The writing, overall, is excellent, if a bit loquacious at times, as it consistently has been since the fourth book (Harry Potter & the Goblet of Fire). The Battle of Hogwarts is appropriately cataclysmic and rousing (especially when Mrs. Weasley comes to the aid of her daughter, Ginny, who's being menaced by Bellatrix Lestrange -- wow, talk about fierce).
The body count, like the denouement, isn't shocking; nor is it too predictable. Rowling has sewed up the Harry Potter saga in a satisfying, character-true manner, with little, if any, room left for more (worthwhile) sequels.
By all means, check it out.