。
She read all night long.
Literal
She [topic-は] all-night book [object-を] read.
A simple, direct narrative sentence. 一晩中 ('all night long') sets the duration; 本を読む ('read books / read a book') is one of the most basic activity-verb collocations; plain past 読んだ reports the completed action. The bare noun 本 is ambiguous between 'a book' and 'books' — Japanese plurals are typically left implicit when not relevant, and context determines the interpretation. Here either reading is fine; the point is that she spent the whole night with reading material.