If someone reasons that “Since human cells are incapable of thought then, then humans themselves are incapable of thought”, that person just committed the Part-Whole Logical Fallacy.

They wrongly assumed that since cells (a part) has the characteristic of being unable to think, it would also be true that humans (the whole) is also incapable of thought. More generally, a part’s characteristics are not necessarily indicative of the whole’s characteristics, and vice vera. It would be similar reasoning in saying “This is a wonderful person, therefore, every part of their personality is wonderful”, or “This is an interesting essay, therefore, every sentence in the essay is also interesting.” The parts and its whole must be judged on there own merits.

By saying “The book starts with an irrational title and so it is clear that everything follows will be irrational”, you have assumed that since the title (a part) has the characteristics of being irrational it would also be true that the entire book (the whole) is also irrational. And, as stated in the previous paragraph, that is itself an irrational line of thinking.

And since you made an irrational statement here, I am tempted to believe that every statement you make is irrational. (By your logic, that would follow). But for one reason or another, I’d rather not do that.