I mean, we literally have a famous idiom in English that you cannot judge a book by its cover...one of the most widely used metaphors in the language, specifically used to remind people that superficial appearance can be deceiving. And it's flanked by several others, like "still waters run deep," "not all that glitters is gold," "beauty is only skin deep," "the clothes do not make the man," "more than meets the eye"....
It's probably one of the most common metaphors in our language, and English isn't alone in this. Judging something on the basis of very limited information, especially if your judgment ends up being truly inaccurate for that thing's actual qualities, is usually considered a fault.
Now, the issue of course is basing a judgment on sufficient information. What's sufficient? How much do you need to know? This is necessarily a sorites paradox. There is no single right answer for all cases; as Aristotle would put it, we must find the value that is correctly intermediate between the extremes of deficiency and excess for each situation, not some singular perfect intermediate value which is universally correct for all cases and all time. It is not possible to have a vice of excess in terms of "making good judgements in general," since a larger number of good judgements is always better than a smaller number of good judgements, but it clearly is possible to have a vice of deficiency in terms of failing to seek out enough information, vs a vice of excess, delaying so long that you effectively fail to make a decision at all. I would consider this a branch of diligence, which is flanked by the deficient vice of sloth, and the excessive vice of perfectionism: on the one hand, lacking in due motivation to properly prepare and investigate, and on the other, becoming so hyper-focused on making perfect decisions or judgments that you end up making no judgment at all ("the perfect is the enemy of the good" and all that.)
You are not wrong to say that you should not need absolutely flawless back-to-front understandings of things in order to make judgments about them. Yet, at the same time, your actual conclusions drawn here appear to be rather at odds with the product itself, such that others have claimed you are asserting simply false things about the book in the process of stating your judgment about it, rendering that judgment questionable. To use an obviously toy, primitive example: if someone said they did not like a particular flavor of ice cream because it was pink and they don't care for bubblegum ice cream, it would not be inappropriate for someone to question that judgment, not because disliking bubblegum ice cream is somehow inappropriate, but because the ice cream is actually strawberry flavored. In other words, the judgment has been made based on a (in this case, axiomatically, by design) inadequate understanding of the item in question. Now, you may certainly argue that there is a difference between this real example and my artificial, toy example, in that (say) one can actually read parts of the text and miss details that only come up later, whereas if one has tasted any amount of the ice cream at all one should quickly recognize what it's supposed to taste like. That's the sorites paradox coming in: what is a heap? When does a sufficient reading of the text fall below the minimum amount of information to draw a conclusion? There will never be a single answer. But that does not mean that there aren't states of insufficient information, nor that all judgments are equally valid on the basis of incomplete readings...especially if those judgments are accurately (that's very important) called out as asserting objectively false things about the text (such as claiming that it contains things it does not, or fails to contain things it actually does contain.)
