From the reviews:

"Read this book just for Erdoes's (Erdos's) characteristic turn of thought, or for results hard to find elsewhere, such as a finiteness theorem concerning odd perfect numbers with a fixed number of factors. Summing Up: Recommended. Lower-division undergraduates through professionals." (D.V. Feldman, CHOICE, December, 2003)

"This is an English translation of the second edition of a book originally published over 40 years ago ... . The contents should be accessible to, and inspire and challenge, keen pre-university students as well as giving the experienced mathematician food for thought. The proofs are elementary and largely self-contained, and the problems and results well motivated. ... This translation makes a very clearly and nicely written book available to many more readers who should benefit and gain much pleasure from studying it." (Eira J. Scourfield, Zentralblatt MATH, Issue 1018, 2003)

"This rather unique book is a guided tour through number theory. While most introductions to number theory provide a systematic and exhaustive treatment of the subject, the authors have chosen instead to illustrate the many varied subjects by associating recent discoveries, interesting methods, and unsolved problems. ... Janos Suranyi's vast teaching experience successfully complements Paul Erdoes's ability to initiate new directions of research by suggesting new problems and approaches." (L'Enseignement Mathematique, Vol. 49 (1-2), 2003)

"This is a somewhat enlarged translation of the Hungarian book ... . It goes without saying that the text is masterly written. It contains on comparatively few lines the fundamental ideas of not only elementary Number Theory: it contains also irrationality proofs ... . The book is hence by far not an n-th version of always the same matter. The style reminds me on the celebrated book of Polya ... . It is desirable that the book under discussion should have a similar success." (J. Schoissengeier, Monatshefte fur Mathematik, Vol. 143 (2), 2004)

"This an introduction to elementary number theory in which the authors present the main notions of that theory and 'try to give glimpses into the deeper related mathematics', as they write in the preface. There are 8 chapters ... . Each of them brings not only the notions and theorems (sometimes with unconventional proofs) which usually appear in introductory texts, but discusses also topics found rarely ... . One also finds several interesting historical comments." (W. Narkiewicz, Mathematical Reviews, 2003j)