(This post, of course, is for those who want to know more about Liberian history than what is freely available on Wikipedia.)
Any number of books on African colonialism have been written, but most of them deal with British, French, Belgian, German, and Dutch colonialism. Few deal with independent countries that had black majority rule during the nineteenth century (Liberia and Ethiopia), and fewer still deal with countries established in whole or in part by freed black American slaves (Liberia and Sierra Leone). However, in addition to books dealing specifically with Liberia, the lessons of some other African nations, even those elsewhere on the continent, are instructive in understanding the stratification of Liberian society, because it long bore an eerie resemblence to that in many of the European colonies of Africa.
The history of Liberia is one of the most fascinating chapters in American history, African history, and black (in Liberia they would say "Americo-Liberian") history. It is not well-known, and is especially poorly understood by non-black Americans. High school and even undergraduate history texts tend to gloss over Liberia with a hasty mention sandwiched somewhere between the War of 1812, the Industrial Revolution, the Maine-Missouri Compromise of 1820, the Mexican-American War, and the Compromise of 1850. In other words, most students either never hear it or would miss it if they sneezed at the wrong moment in class.
Like the Biblical Hebrews, who descended from an early Canaan southward to Egypt, lived through generations of slavery there, and were later led out and back to Canaan (later Israel) by God during the Exodus, the Americo-Liberians descended from the "Pepper Coast" (also known as the "Slave Coast") of West Africa westward to America, lived through generations of slavery there, and were later led out and back to the "Pepper Coast" (later Liberia) by God (theirs was also an explicitly religious mission) during their eastward exodus. I have found two books that are particularly illuminating on the history of the Americo-Liberians both in America and in Liberia:
Alan Huffman, Mississippi In Africa: The Saga of the Slaves of Prospect Hill Plantation and Their Legacy in Liberia Today (Gotham Books 2004). This book tells the true story of an entire plantation of slaves, the owner of which plantation had his will drafted to specifically allow the vast majority of his slaves to choose passage to Liberia if they so desired. After a very protracted legal battle over the intent of the deceased land-owner, the slaves were allowed to emigrate to Liberia, and the author traces their descendants through the intervening century and a half.
James Ciment, Another America: The Story of Liberia and the Former Slaves Who Ruled It (Hill And Wang 2013). This book is mostly focused on the history of Liberia itself, rather than on the origins of the Americo-Liberians. However, when trying to understand the history of a country where the situation is still rapidly evolving, it helps to have a book that takes the story through 2013. This book also provides more detail as to the structure, key players, and gamesmanship involved in the Liberian government over the decades.
In addition, when compiling the notes for this year's jazz curriculum for my home town's music department, I found that a very concise narrative of Liberian history from the 1930s through the Doe and Taylor regimes (and, notably, including the period in the late 1940s during which Ellington was commissioned to write and premiere The Liberian Suite) can be taken from the following book. This title covers the post-colonial history of the entire African continent, but the chapter on Liberia is a very solid one:
Martin Meredith, The State of Africa (Public Affairs 2004).
Similar African Colonial/Post-Colonial Liberation War History
I have also found that the history of the Americo-Liberians relative to the native Liberian tribes bears a startling (and, one could argue, very unsettling) similarity to the history of the white Rhodesian settlers relative to the native Ndebele and Shona tribes of central Southern Africa. Also, the butchery and corruption of the "liberation" governments of Doe and Taylor seem oftentimes to be almost a perversely overindulgent realization of Robert Mugabe's "indigenization" schemes. To that end, the following three books on the history of Rhodesia and Zimbabwe are all terrific, and are written by a reasonably impartial author (a white liberal Rhodesian expatriot who disliked the Smith regime and only fled Zimbabwe when Mugabe ordered his arrest for reporting on the Matabeleland massacres of the early 1980s):
Peter Godwin, Mukiwa: A White Boy In Africa (Atlantic Monthly Press 1996).
Peter Godwin, When A Crocodile Eats The Sun (Little Brown and Company 2007).
Peter Godwin, The Fear: Robert Mugabe And The Martyrdom Of Zimbabwe (Little Brown and Company 2011).