So there are different words for stupid depending on whether we use it upon human beings or objects? טפש and מטומטם. Am i right?
You can say מטומטם about a person. You can't say a book is טיפש but you can say טפשי.
So isn't there any difference between the words?
It's kind of like stupid and dumb. The words are synonyms with very slight variations in meaning.
is there a good reason why "this book is stupid" doesn't work?
because in English I can't think of a difference.
"This book" would be "הספר הזה"
yes, but in english there's no difference in meaning per how you use the copula
or whatever, you can find some wisp of a difference between the two in order to save face
There's no difference in meaning, but that's not what the sentence says.
How about 'a crazy book' ?