Geoff Smith takes a light-hearted yet suitably rigorous approach to the "pure core" of any undergraduate maths program. In addition to dealing with Sets, functions/mappings, Complex numbers, elementary linear algebra in the form of vectors and matrices, group theory and sequences and series (the basis for any course on analysis) this is the only book I've seen with a section on how to write a formal proof. Many introductory level texts teach us how to use proof by induction or contradiction, but Smith goes on to speak about style, form and other things which are so difficult to get undergraduates to do! The book closes with two constructions of the reals and introduces the p-adic numbers. While not suitable for a more advanced course in either analysis or algebra, it provides an excellent introduction to both, as well as a good companion to some other text. With an associated web page providing occasional updates and additions to the material covered, as well as suggestions for further reading, this book will stand you in good stead for further maths courses. All in all, highly recomended - get one today!