On the Edge of the Primeval Forest by Albert Schweitzer is the obvious starting point — Schweitzer's own account of his first years at Lambarene, written in plain prose by a man who saw himself as a doctor rather than a writer. It is short, vivid, and remarkably free of self-importance, considering its author later won the Nobel Peace Prize.
Reverence for Life: The Words of Albert Schweitzer collects the philosophical writing that made him famous in Europe before he came to Africa. Read it after the memoir and the place starts to make a different kind of sense.
The Africa House by Christina Lamb, while set in Northern Rhodesia, captures the same eccentric impulse — a European building an outpost of European life in the equatorial forest — and helps explain why Lambarene still feels the way it does.