'Quantum Cosmology' offers a guided introduction to the quantum aspects of the cosmos. Starting with an overview of early universe cosmology, the book builds up to advanced topics such as the Wheeler–DeWitt equation, gravitational path integrals, and the no-boundary proposal for the wave function of the universe. Readers will explore tunneling processes via Coleman–DeLuccia instantons, the quantum origin of primordial fluctuations, the thermodynamics of horizons, and basic notions of string cosmology. Concepts such as wormholes and semi-classical geometry are introduced with clarity and physical motivation. The book assumes some familiarity with general relativity and quantum mechanics, but little prior knowledge of cosmology. It includes a wide range of exercises, with solutions provided. Written in a pedagogical style, it bridges the gap between undergraduate courses and the research level in this frontier area of theoretical physics.

‘J.-L. Lehners’s Quantum Cosmology provides an excellent review of both the well-established pillars and modern developments in the subject. It's perfectly organized and leads the reader from the basics to the forefront of research. Lehners explains a wide spectrum of complex topics, from the observational universe to the highly mathematical Picard–Lefschetz theory, in simple, accessible language. The useful exercises with solutions at the end of each chapter are a very good complement to the main text. In summary, this book is invaluable for scientists at every stage of their careers. Students will find it a perfect introduction to advanced topics, while young scientists can use it as a springboard to the forefront of quantum cosmology research. For senior scientists, it's an excellent way to quickly refresh their knowledge of complex subjects.’

George Lavrelashvili - Tbilisi State University

‘Quantum Cosmology is a very important subject, arguably the only arena where the challenging and enigmatic field of quantum gravity can currently be confronted with observations and measurements. Yet it has, until now, received only limited treatment in textbook form. This volume, carefully crafted by a leading expert, represents an extremely valuable addition to the literature. Much of the material cannot be found elsewhere at this very accessible, yet technically precise, level. The book will thus serve as an essential resource for lecturers and students alike.’

Arthur Hebecker - Heidelberg University