How do you photoread a very large dictionary or an encyclopedia ?

I have an Italian Dictionary I would like to Photoread but it is almost A4 size and its 700 pages long !

Whats the best way ? - In the home course manual one of the first exercises is to photoread a dictionary for 5 minutes, but that only covers a couple of letters of the alphabet.

Does this mean that you have to do the dictionary in sections or can you do it all at once - I guess that photoreading my 700 page dictionary may take 15-20 minutes ? Is this too long

Does the same principle apply to encyclopedias ?