The classic reference volume is G. E. Bacon’s Neutron Diffraction, but that book is from 1955 and I can’t recommend something that old, but I don’t know of a good replacement. Likewise, Colin Windsor’s Pulsed Neutron Scattering (Taylor and Francis) is also a classic, but much has changed since 1981 when that was published.
International Tables for Crystallography, Volume H: Powder Diffraction (2019), edited by C. J. Gilmore, J. A. Kaduk, and H. Schenk, DOI: 10.1107/97809553602060000115
This is a comprehensive reference on powder diffraction with some material specific to neutron diffraction. Note that if your library does not have a physical copy of this, they may offer on-line access.