Bolivia is not well served by English-language writing, which makes the books that do exist more valuable.
Before you go
The Motorcycle Diaries by Ernesto Che Guevara (1995) — Guevara's road journal from 1952 includes a long section in Bolivia and Peru. The prose is unpolished and the politics are nascent, but it captures something real about travelling through the Andes on almost no money.
A Concise History of Bolivia by Herbert Klein (2003, Cambridge University Press) — the standard academic history, readable for non-specialists. Essential if you want to understand how one of South America's richest silver empires became one of its poorest nations, and why politics here have been so turbulent.
Evo Morales and the Movimiento al Socialismo in Bolivia — various academic and journalistic accounts cover the transformative 2006–2019 period of indigenous-led government. Reading something about this before visiting makes conversations with Bolivians far more interesting.
On the ground
Lonely Planet Bolivia remains the most comprehensive practical guide in English, updated regularly. It covers the whole country in useful detail and is worth having for the regional information even if you don't follow its recommendations religiously.
Fiction and narrative
Our Lady of the Assassins — though set in Colombia, Fernand Vallejo's noir sensibility is useful preparation for South American urban life. For Bolivia specifically, the pickings are slim in English translation.
The Motorcycle Diaries (film, 2004) — Walter Salles's adaptation is worth watching before or after the book. The Bolivian and Peruvian highland sequences are beautifully filmed.