I've been reading large chunks of that and it's both good and bad. The good parts are where he sticks to his core strength of anthropology -- it's filled with fascinating descriptions of how commerce and law worked in various societies, ancient and modern, from the Irish monks who sat down and figured out the precise compensation that you need to pay if one of your bee stings another man [the regular price of the sting minus the cost of the bee] to the spear/cloth bartering festival slash orgies of some Aboriginal tribe. Lots of fascinating stuff there.
He is on much shakier territory when he starts to enter into the economists' domain. He's probably correct when he declares that the inefficient pre-money "barter economy" has never actually existed, but then he breaks his arm patting himself on the back to say he's smarter than all the economists who always use this as an example when explaining why we have money.
When it comes time to actually try to explain debt itself, he's really lost. He starts the book by posing a question: how is it that the language of debt got so wound up in the language of morality; by extension, why do we think it's immoral to not pay our debts? He never seems to come around to the obvious answer: that a debt is a promise, a promise of money later in exchange for money now, and that breaking your promises is seen as immoral because it breaks the reciprocity that underlies almost all human interactions. He seems to have a mental image of "debt" as something that a loan shark puts you in so that he can break your legs afterwards, rather than the vast majority of the world's responsible debt arrangements which wind up beneficial to both parties.
Anyway, I'd say Graeber's "Debt: The First 5000 Years" has some interesting bits but a bunch of flaws. And this comment is only this long because I don't have an account on Amazon.