Translation:They are not reading the book, they are looking at it.
'They do not read the book, but look at it" or they are not reading the book, but are looking at it" are the best translations for idiomatic English.
yes, in English we never would say someone is watching a book. To watch a book is totally incorrect English. You can only see a book or look at it. A native English speaker would laugh if someone said they were watching a book. It indicates you are waiting for the book to do something. Totally wrong translation and should be fixed.
It would prefer, to change the sentences to: hanem megnézik a képek(?)/but they are looking at the pictures. But they watch it - sounds somehow wrong to me.
the proper translation is "They are not reading the book, they are just looking at it."
That translation might cause confusion, since 'just' can be included in the Hungarian sentence as well: "Nem olvassák a könyvet, hanem csak nézik".
see my comment below. your translation is totally wrong. i am a native English speaker and we would never say what you have written.
Is this meant to mean something like "They are not reading the book, just flipping through the pages"?