Would it be fine to use Serge Lang's two Calculus books as textbooks for freshman as Maths major? I'm a freshman in Maths major, but the recommanded textbook(Calculus:A Complete Course by Robert A. Adams) by Prof. of Calculus course is too much expensive, well, I found there're Serge Lang's two Calculus books in second-hand bookstore. is it okay to use these two books as textbook either ?
"A First course in Calculus", Serge Lang, UTM, Springer
"Calculus of Several Variables", Serge Lang, UTM, Springer
 A: Lang's book is great and I heartily recommend it. Unlike the rest of Lang's books, which he has written in order for he himself to learn the subject in question (and which books concern themselves with mathematics of significantly higher level), his Calculus books were written explicitly with the student in mind.
What this means is that it (at least his single-variable book; I haven't read the multi one) is the most well-arranged and pedagogically sane book on Calculus I've come across. Its intended audience consists of serious students who want to learn, but don't necessarily have a lot fo experience with mathematics: the book is more or less self-contained with respect to giving you all the necessary tools you need to solve the problems; it also has the virtue of being sufficiently rigorous and honest in its explanation of the key ideas. Many other textbooks either sacrifice ideas and intuition for logical formalism (Spivak's book is in fact an analysis book in disguise, I believe, so it's not even playing the same game), or they eschew a rigorous and careful treatment of ideas because the authors make no distinction between math being simple and math being easy.
But so, to answer your question, if you want to acquire a good understanding of Calculus, Lang will give you it, and may even give you a better one than other textbooks, if you read him closely enough (the real mathematician's answer of course, is that you go to the library and check out and read several books on Calculus to get an idea of the various perspectives since no one textbook is perfect, though in my eyes Lang's as close to perfect as we have).
