Reading advice for Advanced Calculus by Loomis and Sternberg I am a math major currently in my sophomore year. I have a sound base in one variable calculus and basic linear algebra. I am currently doing a course in multivariable calculus. I have completed reading Calculus by Apostol Vol 1 and 2 and reached nearly half-way through Baby Rudin. 
I am currently thinking about reading Advanced Calculus by Loomis and Sternberg mainly because of its vast table of contents and applications in Classical Mechanics (I am a physics minor too). After going through the first few chapters lightly, I am certain that it would take a whole semester to complete this book.
My question is: Is it worth spending the whole semester (5 months) in this book? 
 A: It depends on what draws you to the text, and what prompts you to post this question:


*

*Is it a matter of (mostly) enjoyment (that the prospect of digging
into Loomis and Sternberg is enticing to you, so the question is more
along the lines, "is it so fun/challenging that it would be a shame
to miss out by not tackling it?"),

*...Or a question of necessity (e.g., Is studying Loomis and Sternberg
in my best interest, mathematically?),

*or both?


It seems to me that, having tackled Apostol I, II, and given that you're currently making your way through Rudin,, you will do just fine, mathematically, if you do not read it, or if you read it "recreationally." Having said that, if having perused its table of contents, you find it immensely appealing, so much so that you're willing to spend "down time" on the text, just for the sheer fun and challenge of it, then go for it! 
To sum up: I do not think that Loomis and Sternberg is a prerequisite that any serious student of math ought to study. But it is certainly a fine text to work through if you you find doing so to be enjoyable, enriching, and/or helpful as a supplement to your current studies. 
