I currently possess Calculus $3$rd edition by Michael Spivak in it's electronic form. However, I am considering buying a hard copy and have the option of buying either a used $3$rd edition or a new $4$th edition.
Since, the $4$th edition is quite costly for me, I want to be absolutely sure before buying. I haven't been able to locate an electronic copy of the $4th$ edition anywhere.
So, would someone be kind enough to tell me precisely the differences between the two books.
I expect to solve a good amount of hard calculus problems so I would choose whichever has more problems.
Thank you for your help.