A reader of Hebrew can learn to read Samaritan quickly, because the two scripts agree on everything except the shapes. The alphabet has the same twenty-two letters in the same order with the same numeral values, the direction of writing is the same, and the language of the Torah text is the same. What has to be learned is a set of twenty-two new forms and a short list of differences, and the differences are the interesting part.
There are no final forms, so the five Hebrew letters that change shape at the end of a word do not change here. There is no dot inside a letter and no dot on top of one, so the distinctions the square script marks that way, hard against soft and sh against s, are not written and are carried by the reading tradition instead. Words are separated by a written mark rather than only by space. And the letter names are not all the ones a Hebrew reader knows: six of the twenty-two differ, and each difference records something about how the community says the letter.
The largest adjustment is not on the page. It is that the text being read is not the same text. The Samaritan Pentateuch differs from the Masoretic text in a great many places, so a reader who knows the Torah by heart in one tradition will find the other saying something else more often than they expect. That is the point at which reading the script stops being a matter of decoding letters and starts being a matter of reading a different book.