Like the phenomenon it describes, the book before you has followed a long, winding path. The first discussions of putting it all together took place around 1995, when the gamma-ray burst (GRB) field started to mushroom. Not quite a score years later, we have still not caught up. In the last forty years, GRBs have engulfed the entire electromagnetic spectrum and entrenched on supernovae, extragalactic astronomy, nucleosynthesis in the cosmos, observational cosmology, and multi-messenger astronomy. As their perspective zoomed out, the once lone observers now banded in large collaborations, bringing together a huge arsenal of ground- and space-based observatories. GRB-designed missions were flown, adding large volumes of data. Observers are now faced with the embarrassment of riches and the reality of an everlasting mystery. Theories followed observations, originally dealing with the big picture, then gradually focusing on smaller pieces of the GRB puzzle, as – sometimes controversial – evidence gathered. It is still disputable what are the facts, the maybe's and the unknowns in GRBs.

GRBs exploded onto the astrophysical scene in 1973, when the discovery of a new, strange phenomenon, was announced: brief, intense flashes of gamma rays that, for the most part, occur in unpredictable places in the sky at unpredictable times and are never seen again. It had taken the discoverers about half a decade of labor to gather up enough data from the Vela satellites to convince themselves that the phenomenon was indeed astrophysical.