There doesn't seem to be one.
There are some older books from the 1970s and '80s, and a "Political History of Zambia" published this decade. But that's about it. A general history of the country since independence, published in the last 20 years? Doesn't seem to exist.
So there's a niche for some aspiring young academic. Meanwhile, digging around at the local bookstore and the museum and online has turned up some interesting nuggets.
-- Zambia was central to a dispute between Britain and Portugal in 1890. The Portuguese wanted to claim it to connect their colonies in Angola and Mozambique. AFAICT, they had a decent claim. But the British completely curb-stomped them, threatening to take away Mozambique if Portugal didn't retreat and withdraw their claim. Which they did, albeit with considerable and lingering resentment.
-- That said, Zambia remained a complete and utter backwater until the 1920s, when copper was discovered. It was the distant northern frontier of the British Empire in South Africa. There was one rail line, a handful of white farms, and absolutely nothing of interest. All of that changed when the copper -- some of the world's richest deposits -- was found. By WWII Zambia ("Northern Rhodesia") had 30,000 white settlers and the region's economy had been reconfigured around providing cheap labor for the mines.
-- For a decade, 1953-63, Zambia was part of the short-lived Federation of Rhodesia and Nyasaland, a state now completely forgotten except by historians and a dwindling handful of cranky white ex-settlers. (I'm still at a loss as to what the point of this entity was, but maybe more reading will make it clear.)
-- Zambia pretty quickly developed a postwar nationalist / independence movement, which seems to have split early on between "independence for Zambia" and "independence for all white-dominated South Africa" factions -- basically UNIP (which would eventually rule Zambia) and the more well-known African National Congress.
The independence struggle was, in the cold light of history, rather less violent and bloody than it could have been. The death toll seems to have been in the hundreds rather than the thousands, which was fairly light compared to some of Zambia's neighbors (Mozambique, Angola, Rhodesia / Zimbabwe).
That said, there were some gruesome incidents. In the Lusaka museum, I came across a fading photograph of Mrs. Lillian Burton. She and her two small daughters were pulled out of a car and horribly killed in 1960. The museum article made it sound like a wrong-place-wrong-time kind of a thing, but this interview suggests that it was deliberate murder on the part of UNIP ("Our final decision was to kill someone who was well-known in the streets of London and there could not have been any better figure than Ms Lillian Burton who was very popular in Zambia.")
The chachacha period is familiar, and kind of depressing. It wasn't Rhodesia/Zimbabwe, but the center did not hold, and in the end the country was handed over to a bunch of guys who didn't really know what they were doing. A common enough story, but still.
-- At independence, there was one of those crazy religious movements. It was anti authority -- all authority, colonial and post-colonial alike. Led by a female seer, Alice Lenshina. Melded Christian and animist elements, immunity to bullets, the works. Ended badly.
-- After independence, Zambia embarked on a policy of supporting black independence movements all across southern Africa. This did not meet with approval from its white-dominated neighbors. The Rhodesians staged a number of border incursions, and the South Africans initiated "Operation Plathond" to create and support a fairly insane and pointlessly destructive guerrilla movement in the country's northwest.
-- Kaunda wanted the Bomb, which is why Zambia was one of a handful of countries to vote against the Nuclear Non-Proliferation Treaty in the UN back in the late 60s. Why? Because he knew South Africa had it. (How? Not clear, but my guess would be he made the various independence movements he hosted pay their rent with, among other things, intel.) It's not clear if he seriously thought the South Africans would nuke Lusaka, but presumably he thought a nuclear deterrent would make them think twice about it.
-- And finally, Zambia may hold a record of some sort: four serious coup attempts (1980, '88, '90 and '97) without a single success.