enchiridion
/ˌɛnkʌɪˈrɪdɪən
/noun (plural enchiridions or enchiridia /ˌɛnkʌɪˈrɪdɪə/) formal
A book containing essential information on a subject.I also wrote a book on Faith, Hope, and Charity, at the request of the person to whom I addressed it, that he might have a work of mine which should never be out of his hands, such as the Greeks call an Enchiridion (Handbook).
Origin
Late Middle English: via late Latin from Greek enkheiridion, from en- 'within' + kheir 'hand' + the diminutive suffix -idion.