。
You shouldn't eat while reading a book.
Literal
Book [object-を] read-[while-ながら] meal [object-を] do-[forbidden-てはいけません].
Combines ~ながら ('while') with the polite prohibition ~てはいけません. 食事をする ('to have a meal,' literally 'do meal') is the standard verbal form for eating a proper meal, a light-verb construction using the noun 食事 with する. A typical piece of table-manners advice, usually from parent to child.