"Elasticsearch - The Definitive Guide," authored by Clinton Gormley and published by O’Reilly Media, is announced as an early release to assist both novices and experienced users in navigating the complex world of Elasticsearch, a new technology with familiar concepts. The guide, accessible online and available in print and eBook formats, is designed to help users with a programming background, including those with SQL or database experience, by explaining concepts from first principles. Emphasizing the importance of free access, the book is available for online reading to ensure broad accessibility, with O’Reilly Media supporting this open-source initiative. Although the book is still in progress, with new chapters being added regularly, it is already considered valuable for many users, and the authors encourage contributions and suggestions through GitHub.