Short answers, pulled from the story.
Mythic Odysseys of Theros was officially announced on the 2nd of March 2020 after being leaked through an Amazon product listing. The book was originally scheduled for release on the 2nd of June 2020 but was delayed due to printing issues caused by the COVID-19 pandemic.
The Mythic Odysseys of Theros sourcebook was developed by James Wyatt and F. Wesley Schneider. James Wyatt is a veteran of the Dungeons & Dragons development team who began writing free PDF releases known as Plane Shift in 2016 to adapt Magic: The Gathering planes for D&D.
Mythic Odysseys of Theros introduces two new races called the satyr and the Leonin alongside three reprinted races including the centaur, the minotaur, and the Triton. The satyr is a half-human half-goat creature associated with music and revelry while the Leonin are a proud feline race from Magic: The Gathering.
The Piety system in Mythic Odysseys of Theros tracks a character's relationship with the gods and influences their abilities and the outcomes of their actions. This system is complemented by an omen chart that predicts divine intervention and a new supernatural gift ability chosen during character creation.
The hardcover version of Mythic Odysseys of Theros was released on the 21st of July 2020 due to printing delays caused by the COVID-19 pandemic. The book is also available as a digital product through Wizards of the Coast licensees such as D&D Beyond, Fantasy Grounds, and Roll20.