there are imperfective and perfective forms of each verb yes? and the imperfective is czytac / czytam czyta etc , but i read that the perfective form is used to descrive a finshed state like " i have read a book " instead of czytam ksiazke ( reading a book . so woudnt you use the perfective form of czytac instead of przeczytasz ?
There are perfective and imperfective aspects of MOST, but not all verbs. Whether a verb is perfective or imperfectvie is already known (at least to a native speaker) in the infinitive. There is no perfective form of czytać, it is always imperfective. It is the prefix that makes an imperfective verb perfective.
However, a prefix does not always indicate the perfective aspect. Eg zabić (perfective), zabijać (imperfective) to kill. Bić alone means to hit or strike, adding the za- changes its meaning to kill.
Sorry for all this grammatcial mumbo-jumbo, but it's no exaggeration that Polish is a complicated and difficult tongue for non-natives.