I was thinking of something today that Eliot either wrote or said
about thanking people for a gift of a book. This is a great time to
spread the word. Eliot said to write a note of thanks right away.
That way you can tactifully avoid making a comment on what you think
of the book.
I'm pretty sure that I read this in the book "Affectionately, T.S. Eliot"
but I was unable to find it to quote it directly.
William Turner Levy and Victor Scherle, "Affectionately, T.S. Eliot"
J.B. Lippincott, New York, 1968