  PRIMA (The PRobe for-Infrared Mission for Astrophysics) is a concept for a
far-infrared (IR) observatory. PRIMA features a cryogenically cooled 1.8 m
diameter telescope and is designed to carry two science instruments enabling
ultra-high sensitivity imaging and spectroscopic studies in the 24 to 235
microns wavelength range. The resulting observatory is a powerful survey and
discovery machine, with mapping speeds better by 2 - 4 orders of magnitude with
respect to its far-IR predecessors. The bulk of the observing time on PRIMA
should be made available to the community through a General Observer (GO)
program offering 75% of the mission time over 5 years. In March 2023, the
international astronomy community was encouraged to prepare authored
contributions articulating scientific cases that are enabled by the telescope
massive sensitivity advance and broad spectral coverage, and that could be
performed within the context of GO program. This document, the PRIMA General
Observer Science Book, is the edited collection of the 76 received
contributions.

Instrumentation and Methods for Astrophysics