Having used this book both as an MSc level text book and as a technical reference book in the commercial sector, I can strongly recommend "Principles of Geographical Informations Systems" as a must for any serious GIS user's book shelf. Suitable for any level of GIS experience, it is well-structured, easy to understand and, most importantly, technically strong. It successfully introduces the fundamental principles of GIS, as well as extensively tackles more technical issues such as the use of spatial statistics in interpolation, error propagation and fuzzy set theory.