Recommend Chang Gengzhe's Course of Mathematical Analysis. The language is approachable, which is extremely rare in mathematics textbooks. Just entering the transitional stage of higher education is a good choice. The prototype of the first edition is the HKUST textbook for teenagers, which is famous for its difficulty in exercises, but the difficulty of exercises in the new edition has dropped greatly. Suitable for self-study. Zhang Zhusheng's New Lecture Notes on Mathematical Analysis is often recommended as a self-study book because of its conciseness, but the biggest problem with this book is that it has no exercises. If you must read it, you must cooperate with the set of mathematical analysis exercises of Peking University.