Hunter is in the abandoned library reading the Book of Poems, he is offered this other book by The Library Guy.  Hunter later rediscovers the same book in the school library with the help of Andres. 
It is actually a real poem written by Decimus Magnus Ausonius, from Idyllia  and is referred to in Descartes dream.
A translation reads:
IV. THE PYTHAGOREAN " YEA " AND " NAY "
"YES" and "no": all the world constantly uses these familiar monosyllables. Take these away and you leave nothing for the tongue of man to discuss. In them is all, and all from them ; be it a matter of business or pleasure, of bustle or repose. Sometimes two parties both use one word or the other at the same time, but often they are opposed, according as men easy or contentious in character and tempera- ment are engaged in discussion. If both agree, forthwith " Yea, yea " breaks in ; but if they dispute, then disagreement will throw in a "Nay." From these arises the uproar which splits the air of the courts, from these the feuds of the maddened Circus and the wide-spread partizanship which fills the tiers of the theatre, from these the debates which occupy the Senate. Wives, children, fathers, bandy these two words in peaceful debate without unnatural quarrelling. They are the instruments with which the schools fit for peaceful learning wage their harm- less war of philosophic strife. On them the whole throng of rhetoricians depends in its wordy contests : " You grant that it is light ? l Yes ? Then it is day ! " " No, the point is not granted ; for whenever many torches or lightning-flashes give us light by night, yes, it is light ; but that is not the light of day." It is a case of " yes " and " no " then ; for we are bound to say: "Yes, it is light," and "No, it is not day." There you have the source of countless squabbles : that is why some nay, many pondering on such things, smother their gruff protests and bite their lips in raging silence. What a thing is the life of man which two mono- syllables toss about !
When held by the Library guy, it appears to have a brown cover similar to the first cover of the Book of Poems, however the book found by Anders and Hunter has a green cover similar to the second cover of the Book of Poems raising the possibility that both books are the same.