There has not been a book on the many facets of solar activity, solar variability, and space weather published in the last decade. The present suite of observations (e.g., Solar Dynamics Observatory) and those being developed in the near future (while the book is being developed, such as Parker Solar Probe and Solar Orbiter) drive the need for an update. Further, we are advancing a picture of the Sun that is critical for our technologically-driven society. As such there is a strong desire to raise awareness of solar physics and solar variability, and the Sun-Earth connection within (and outwith) the astronomical/astrophysical community and public sector. The purpose of the book is to demonstrate the present depth of understanding of solar variability. Further, we need to convey why it is critical to augment that understanding - the growing reliance of our planet on electronic technology (ground and space based) which is susceptible to solar activity. The book will bring together observations and observational data in a coherent, consistent fashion.