Is it permissible to read Qur'anic verses from Islamic books without performing ablution (wudu')?

It is permissible by consensus for one in a state of minor ritual impurity (hadath asghar) to recite the Qur'an, whether by heart, or from the Mushaf without touching it, or from books of exegesis. This is based on the hadith of Aisha (may Allah be pleased with her): "The Messenger of Allah (peace be upon him) used to remember Allah in all his states," and the hadith of Ali (may Allah be pleased with him): "The Messenger of Allah (peace be upon him) used to teach us the Qur'an in all circumstances as long as he was not in a state of major ritual impurity (junub)." Muslims have unanimously agreed on the permissibility of reciting the Qur'an for one who is ritually impure, though purification is preferable.