Translation:If you read that entire book, you will be smarter.
Probably not, it would be better to try one of the recommended textbooks.
The main difference is that in English IF is a conditional conjunction and WHEN is a temporal conjunction. In Czech POKUD/JESTLI are conditional, but KDYŽ can be both and sometimes it is clear which one it is and sometimes it is not. It differs for different tenses.
Když ho uvidím... If I see him....
Když jsem byl mladý... When I was young...
Ahoj, Vlado. I don't understand the logic of separating the noun clause "that entire book" with the verb. Isn't it usual to keep all the relevant adjectives with the noun? Is this a common construction in Czech? (My Czech tutor is on holiday and I can't ask her to explain this.)
Celou is a complement https://en.wikipedia.org/wiki/Complement_(linguistics) in this sentence, it is not just an attribute of the noun (kniha), it does expand the object kniha but it is also expands the predicate (the verb přečíst). It also exist in English, but in different sentences (see the link).