1
general::
Study or learn by reading, as in I don't know much about childhood illnesses, but I can always read up on them. [First half of 1800s]
American Heritage Idioms
2
general::
Phrase(s): read up (on someone or something)
to find and read some information about someone or something. • Please go to the library and read up on George Washington. • I don’t know anything about that. I guess I need to read up.
McGrawhill's American Idioms And Phrasal Verbs