The face will only ever be a yellow smiling face at any one time in the medical field. You only get one book to research for every day you work. The face will become not happy if you skip a day.
Something to note is that these books do not accumulate. It will change every day to be a new book with a new number at the end of the title.
Also, I'm moving this thread to the career board since it's about a specific career.