How much of a surprise is it to find what Boo Radley is really like? Has the story before this point prepared the reader for this discovery?

Boo's presence, appearance, and demeanor is a complete surprise to the reader. This larger than life phantom was no more than a slender man, who'd been cooped up far too long. The appearance of the real Boo was unworthy of the legend he'd become.

As I pointed he brought his arms down and pressed the palms of his hands against the wall. They were white hands, sickly white hands that had never seen the sun, so white they stood out garishly against the dull cream wall in the dim light of Jem’s room.I looked from his hands to his sand-stained khaki pants; my eyes traveled up his thin frame to his torn denim shirt. His face was as white as his hands, but for a shadow on his jutting chin. His cheeks were thin to hollowness; his mouth was wide; there were shallow, almost delicate indentations at his temples, and his gray eyes were so colorless I thought he was blind. His hair was dead and thin, almost feathery on top of his head.