Finally, an excellent introduction into abstract/pure mathematics for nonmathematicians. This book fills an important niche for self learners who are interested in pure mathematics but feel that many of the so-called introductory text do not adequately explain the material for the beginner without additional guidance. The problem sets and their detailed solutions provide such a nuanced and profound understanding  than I have been unable to find elsewhere. I look forward to more such books on other fundamental abstract mathematics topics from Dr. Warner such as analysis, abstract algebra, topology, etc.