This book has a long history of more than 20 years. The first attempt to
write a monograph on information-theoretic approach to thermodynamics
was done by one of the authors (RSI) in 1974 when he published, in the
preprint form, two volumes of the book "Information Theory and
Thermodynamics" concerning classical and quantum information theory,
[153] (220 pp.), [154] (185 pp.). In spite of the encouraging
remarks by some of the readers, the physical part of this book was never
written except for the first chapter. Now this material is written
completely anew and in much greater extent. A few years earlier, in
1970, second author of the present book, (AK), a doctoral student and
collaborator of RSI in Toruli, published in Polish, also as a preprint,
his habilitation dissertation "Information-theoretical decision scheme
in quantum statistical mechanics" [196] (96 pp.). This small monograph
presented his original results in the physical part of the theory
developed in the Torun school. Unfortunately, this preprint was never
published in English. The present book contains all these results in a
much more modern and developed form.