This commentary on the Torah is not particularly easy to follow, nor is it particularly rationalistic. The Baal Haturim was written in the 14th century, and uses gematria (numerology based on numbers assigned to Hebrew letters) to tease meaning out of the Torah. For example, the Torah notes that Jacob lays his right hand on Ephraim “though he was the younger” (Gen. 48:14) and Ephraim is to Jacob’s left. Baal Haturim notes that the gematria of the phrase “though he was the younger” (yhu hatzir) is equivalent to “he humbled himself” and therefore treats this as an allusion to Ephraim’s humility, which in turn means that Ephraim merited to have Joshua as a descendant.
Baal Haturim also relies heavily on words that are used multiple times in the Hebrew Bible. For example, Abraham asks the guests to take bread “that will satisfy your heart” (Genesis 18:5). The word for “your heart” that is used here is libchem. Usually “lev” is the Hebrew word for heart, so this is curious. Baal Haturim notes that the word “libchem” is used only a few times in the Bible. One of those times is a reference to people’s hearts rejoicing in Isaiah. Baal Haturim uses this as a reason to go off on a tangent, suggesting that Abraham’s heart rejoiced when he saw the guests, and adding that before the angels/men came Abraham “felt pain in his heart” because of his inability to satisfy any wayfarers.
What makes this book useful if you don't find any of this persuasive? I often hear midrashim (legends) that don't seem to follow from the text of the Torah. Reading Baal Haturim gives me a better sense of how Jewish scholars came up with these ideas.