'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