Recent reading about galaxies and related cosmology.
Galaxies - A Very Short Introduction
John Gribben, 2008, Tigard 523-112 GRI
Like most of the "Short Introduction" booklets, much tightly organized information in about 100 pages. A good quick reference, though I prefer longer books with more journal citations, leading to the original arguments and observations that led to current theories.
Like most cosmologies, the underlying assumptions are simple symmetric models, with fitting parameters like dark matter, dark energy, the inflaton, and other fashionable unobservables. The stubborn refusal of the universe to provide any direct evidence of these fitting parameters, as opposed to alternate unfashionable fitting parameters, suggests we should be looking for anomalies and disconfirming evidence, not support for popular hypotheses. A hypothesis based on three generations of academic belief and no direct supporting data is theology, not science.
Huge sensors outside the atmosphere, orbiting far from the noisy Sun and its deep gravity well, are the most likely source of new data, supporting or contradictory. Launch loop will launch the components of those sensors someday.