Learn Spanish (Latin America): Me gustaría entender este libro incomprensible. - I would like to understand this incomprehensible book.

You could say Este libro me resulta incomprensible (This book is/seems incomprehensible to me). Using resultar here acts as a "pseudo-copulative" verb. This means it connects the subject (este libro) to an adjective (incomprensible) just like ser or estar would, but it specifically adds your personal, subjective evaluation of the book.

Why do we use the infinitive entender here instead of a subjunctive form?

Even though expressions of desire like me gustaría often trigger the subjunctive, that only happens when you want someone else to do something (for example, Me gustaría que entendieras, meaning "I would like you to understand"). Because you are the one who wants to understand here, there is no change of subject, so you must use the infinitive.

Why is the adjective incomprensible placed after the noun libro?

In Spanish, descriptive adjectives that classify or distinguish an object (telling us this is the incomprehensible book, not the easy one) go after the noun. Placing it before the noun (este incomprensible libro) is grammatically possible but sounds much more poetic or dramatic, emphasizing its incomprehensibility as an inherent, defining trait.

Is the word incomprensible related to comprender or entender?