Volume 1 is the most famous entry point. It is renowned for its "spiral approach," where topics are introduced intuitively and then revisited with increasing rigor.
: Defined via step functions before introducing derivatives. solucionario calculo tom apostol vol 1 y 2l old version
If you find yourself copying the solution manual verbatim for three consecutive problems, stop. You are wasting the book. Volume 1 is the most famous entry point