@Jasmine Depends on what type of book you're asking for. I used to use the Arihant one by Amit Agarwal for Calculus for learning tricks needed for JEE problems. However I read other books too on Calculus which helped in letting me go beyond what was mentioned in the Arihant book. If you're looking for a book with only very hard questions, the Sameer Bansal book is the best. However, it is folly to use the Sameer Bansal book unless you are very, very, very good.
For practice, I would first solve the worksheets given, then go to archives, then solved examples after each chapter in the Arihant book (these solved examples were much harder than the illustration problems in the chapter). And finally, I would use the Sameer Bansal book
@Jasmine Buy the Amit Agarwal book first and see if you can solve all the illustration problems (they are quite good for learning tricks used in the JEE). And then you could follow the order I suggested. I don't really think you'd get much time left after solving all these. If you do get time, then move to Sameer Bansal's book.
Having said all this, let me add that I by no means am an expert in all this. The only difference between you all and me and Samjoe is that we've gone through the process, and that you all are going through the process. The best persons to ask are your professors; they would know your levels better, and they have much, much, much more experience than Samjoe and me
@Jasmine Hmmmm... Then stay with it unless you feel that the book is too simple for you, and that it isn't really helping you solve harder JEE level questions.
@Ishan $\sum_{r=1}^{n} \frac{r^4}{(2r-1)(2r+1)} = \sum_{r=1}^{n} \frac{r^2}{4}+\sum_{r=1}^{n}\frac{1}{16(2r-1)(2r+1)}$ where second one telescopes easily
@samjoe Agreed. But for me polynomial division is quite tiresome, so I usually use it as the last resort, especially since both our methods will yield the same result.
@abcd if you divide a number less than $23$ by a number greater or equal to $23$ you get a number in $(0,1)$, that means these numbers cant be our answer