From Shin Kanzen Master JLPT N1 Grammar:
I thought that 出す always follows を, i.e. you (subject) take out something (object).
Is it because 本 is emphasized in this sentence, similar to how が is used instead of を with the potential form of a verb?
Or is it because 出しっぱなしだ as a whole acts more like an adjective that describes the book?