For whatever reason, you must read a book
about macroeconomics, commercial laws, or else.
Your knowledge is very limited in the subject,
and you know in advance that right at the beginning,
you will be facing sentences you will not understand.
Suppose that the reason is that
you aren't very familiar with the vocabulary.
Vocabulary is often the main obstacle to
reading a new book on an unfamiliar subject.
Now, going through the vocabulary of the whole industry
or a broad topic like the laws would not make sense.