Name the fallacy committed in the following: “All the textbooks are books…

The syllogism commits the fallacy of Undistributed Middle. In a valid categorical syllogism, the middle term must be distributed at least once. Here, the middle term is 'books intended for careful study'. In the first premise ('All textbooks are...'), it is a predicate of an affirmative statement, so it is undistributed. In the second premise ('Some reference books are...'), it is also a predicate of an affirmative statement, so it remains undistributed. Since the middle term is never distributed, no valid connection can be established between the subject and predicate terms.