Susskind is much more advanced. Realistically speaking you need to understand and internalize the content of Lewin (or comparable) before you take on Susskind.

Susskind is much more advanced. Realistically speaking you need to understand and internalize the content of Lewin (or comparable) before you take on Susskind. Lewin = undergraduate-level physics Susskind = graduate-level physics, converted to minimize math and maximize accessible explanations, but still graduate-level physics.