Bauhaus by Frank Whitford (1984) is the standard introduction to the movement — its history from Weimar to Dessau to Berlin, its key figures, and its ideas. Whitford writes clearly and without jargon; by the time you arrive at the Bauhaus Building you will have a solid sense of what you are looking at and why it mattered.
Bauhaus: Crucible of Modernism by Elaine Hochman (1997) focuses on the political and personal tensions inside the school — the arguments over what art and design should be for, the pressure from the Nazis, the internal feuds that drove some of the best teachers out. It reads more like a story than an art history text and makes the Dessau buildings feel inhabited.
From Bauhaus to Our House by Tom Wolfe (1981) is a polemical attack on modernist architecture and its legacy — which makes it a useful foil before visiting. Wolfe is funny and often unfair, but the essay forces you to think about what was actually gained and lost when the Bauhaus aesthetic conquered the postwar world. Read it on the train and argue with it while you walk around.
Bauhaus by Magdalena Droste (multiple editions, most recently 2019) is the comprehensive reference published by the Bauhaus-Archiv in Berlin. It covers every workshop, every teacher, every major work in depth, with excellent photographs. Too heavy to carry on the trip, but worth reading before or after — and a good resource if you want to go deeper on any specific figure or period.