Here are two excellent books that read well and can also serve as reference resouces on the subject of the Lakota and their land.
The Lakotas and the Black Hills by Jeffrey Ostler
Wounded Knee: Party Politics and the Road to an American Massacre
by Heather Cox Richardson
If you want a good summary of Lakota history and an explanation of the status of their claim on their land, the Jeffrey Ostler book is for you. The first part is the sad story of the unequal military and bargaining power of the Lakota western plains natives and the "overlanders". The second part is the century long history of the Lakota’s attempts to recover the land. It explains the pertinant judicial cases and legislative initiatives and shows how these have evolved through generational changes in tribal leadership, legal representation and public opinion.
"Wounded Knee.." by Heather Cox Richardson overlaps one time segment of the Ostler book but there is no overlap in content. While Ostler describes the government’s response to the economic benefits of the Lakota land, Richardson focuses how the land was central to the political needs of President Harrison. Besides the need to placate the mining and ranching interests, Harrison saw the land as essential to his re-election.
Harrison needed the electoral votes that only states could deliver. Creating two States instead of one from the Territory had the further benefit of four and not just two reliably Republican senators. To get sufficient land mass for two states, the land already given to Lakota by treaty was needed. Richardson shows the pressure and deception involved in getting this land and getting it in time to meet the Harrison’s electoral need. She shows the stress on the Lakota people was due to the land issues in that malnutrition and disease resulted from the disappearing buffalo and the diminished treaty-promised rations. Richardson shows how this led to Wounded Knee.
What is encouraging here is the evolution in public opinion. Over the years people have grown in the understanding of the plight of the Lakotas. Ostler provides a quote from the Lakota, Lone Horn (p. 67) that summarizes the attitude of his day: "This is our land yet you blame us for fighting for it." This attitude permeated the judiciary and legislative bodies the first generation of Lakota plaintiffs faced. Today, there is agreement that the Lakotas have been wronged and the issues surround how to address it.
Both these books are not only well written for the general reader, they can also serve as reference books. Since the authors have culled the content to keep to their respective theses, you want more background on a number of issues they bring up. Both are well footnoted to primary and secondary sources.